This is a documentation version of GNU Gama 1.14.

   Copyright (C) 2003, 2013 Aleš Čepek.

   Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts. A copy of the license is included in the section entitled "GNU
Free Documentation License".

Table of Contents
*****************

GNU Gama 1.14
1 Introduction
  1.1 Download
  1.2 Install
  1.3 Program `gama-local'
    1.3.1 Reductions of horizontal and zenith angles
  1.4 Reporting bugs
  1.5 Contributors
2 XML input data format for `gama-local'
  2.1 Angular units
  2.2 Prologue
  2.3 Tags `<gama-local>' and `<network>'
  2.4 Network description
  2.5 Network parameters
  2.6 Points and observations
  2.7 Points
  2.8 Set of observations
  2.9 Directions
  2.10 Horizontal distances
  2.11 Angles
  2.12 Slope distances
  2.13 Zenith angles
  2.14 Height differences
  2.15 Control coordinates
  2.16 Coordinate differences (vectors)
  2.17 Example of local geodetic network
3 SQL schema, SQLite and `gama-local'
  3.1 Working with SQLite database
  3.2 Units in SQL tables
  3.3 Network SQL definition
  3.4 Table `points'
  3.5 Table `clusters'
  3.6 Table `covmat'
  3.7 Table `obs'
  3.8 Table `coordinates'
  3.9 Table `vectors'
  3.10 Example of local geodetic network in SQL
4 Network adjustment with `gama-local'
  4.1 Approximate coordinates
  4.2 Gross absolute terms
  4.3 Parameters of statistical analysis
  4.4 Test on the reference standard deviation
  4.5 Information on points
  4.6 Adjusted observations and residuals
  4.7 Identification of weak network elements
  4.8 Estimation of real errors
  4.9 Test on linearization
5 Data structures and algorithms
  5.1 Observation data and points
  5.2 Supported ellipsoids
  5.3 Transformation from spatial to geographical coordinates
  5.4 Class `g3::Model'
Appendix A Copying This Manual
  A.1 GNU Free Documentation License
    A.1.1 ADDENDUM: How to use this License for your documents
Concept Index


GNU Gama 1.14
*************

1 Introduction
**************

GNU Gama is a project dedicated to adjustment of geodetic networks.  It
is intended for use with traditional geodetic surveyings which are
still used and needed in special measurements (e.g., underground or
high precision engineering measurements) where the Global Positioning
System (GPS) cannot be used.

   In general, surveying is the technique and science of accurately
determining the terrestrial or three-dimensional spatial position of
points and the distances and angles between them.(1)

   Adjustment is a technical term traditionally used by geodesists and
surveyors which simply means "application of the least squares method to
process the over-determined system of measurements" (statistical
methods other than least squares are used sometimes but are not
common). In other words, we have more observations than needed and we
are trying to get the best estimate for adjusted observations and/or
coordinates.

   "Adjustment of geodetic networks" means that we have a set of points
with given coordinates coordinates of some points and a set of
observations among them. What is typical of adjustment of special
geodetic measurements is that the resulting linearised system might be
singular (we can have a network with no fixed points) and we are not
only interested in the values of `adjusted parameters and observations'
but also in the estimates of their covariances. This is what Gama does.

   Gama was originally inspired by Fortran system Geodet/PC (1990)
designed by Frantisek Charamza. The GNU Gama project started at the
department of mapping and cartography, faculty of Civil Engineering,
Czech Technical University in Prague (CTU) about 1998 and its name is
an acronym for _geodesy and mapping_.  It was presented to a wider
public for the first time at FIG Working Week 2000 in Prague and then
at FIG Workshop and Seminar at HUT Helsinki in 2001.

   The GNU Gama home page is

                  `http://www.gnu.org/software/gama/'

and the project is hosted on

               `http://savannah.gnu.org/git/?group=gama'

   GNU Gama is released under the GNU General Public License and is
based on a C++ library of geodetic classes and functions and a small C++
template matrix library `matvec'. For parsing XML documents GNU Gama
calls the `expat' parser version 1.1, written by James Clark. The
`expat' parser is not part of the GNU Gama project, and is simply used
by GNU Gama.

   Adjustment in local Cartesian coordinate systems is fully supported
by a command-line program `gama-local' that adjusts geodetic (free)
networks of observed distances, directions, angles, height differences,
3D vectors and observed coordinates (coordinates with given
variance-covariance matrix).  Adjustment in global coordinate systems
is supported only partly as a `gama-g3' program.

   ---------- Footnotes ----------

   (1) Wikipedia, `http://en.wikipedia.org/wiki/Surveying'

1.1 Download
============

GNU Gama  can be found in the subdirectory `/gnu/gama/' on your
favourite GNU mirror (http://www.gnu.org/prep/ftp.html) or checked-out
from the GIT. See our project page at savannah
(http://savannah.gnu.org/projects/gama/) for more information.

   To get an anonymous read-only access to the GIT repository for the
latest GNU Gama source, issue the following command

     git clone git://git.sv.gnu.org/gama.git

The collection of sample networks is available separetely. To checkout
the `gama-local' examples from GIT use the command

     git clone git://git.sv.gnu.org/gama/examples.git

1.2 Install
===========

GNU Gama is developed and tested under Debian GNU/Linux
(`http://www.debian.org/').  A static library `libgama.lib' and
executables are build in folders `lib' and `bin'.  You can compile Gama
easily yourself if you download the sources.  If `expat' XML parser is
installed on your system, change to the directory of Gama project and
issue the following commands at the shell prompt

     $ ./configure
     $ make

   To run tests from the Gama test suite try

     $ make check

If the script `configure' is not available (which is the case when you
download source codes from a git server), you have to generate it using
auxiliary script `autogen.sh'.  To compile and build all binaries. Run

     $ ./configure [--bindir=DIR --infodir=DIR]
     $ make install

if you want also to install the binaries. You can use configure
parameters if you need to change directories where user executables and
info documentation should be installed.

   Typically, if you want to download (*note Download::) and compile
sources, you will run following commands:
     $ git clone git://git.sv.gnu.org/gama.git gama
     $ cd gama
     $ ./autogen.sh
     $ ./configure
     $ make
   You should have `expat' XML parser and SQLite library already
installed on your system.  For example to be able to compile Gama on
Ubuntu 10.04 you have to install following packages:
     make doxygen git automake autoconf libexpat1-dev libsqlite3-dev

   To compile user documentation in various formats (PDF, HTML, ...) run
the following commands (before you have to run at least `./configure').
     $ cd doc/
     $ make download-gendocs.sh
     $ make run-gendocs.sh
   The documentation should be in `doc/manual' directory.  To compile
API documentation run
     $ doxygen
   in your `gama' directory.  Doxygen output will be in the `doxygen'
directory.

1.3 Program `gama-local'
========================

Program `gama-local' is a simple command line tool for adjustment of
geodetic _free networks._ It is available for GNU Linux (the main
platform on which project GNU Gama is being developed) or for MS
Windows (tested with Borland compiler from Borland free command line
tools and with Microsoft Visual C++ compiler; support for Windows
platform is currently limited to maintaing compatibility with the two
mentioned compilers).

   Program `gama-local' reads input data in XML format (*note XML input
data format for gama-local::) and prints adjustment results into ASCII
text file. If output file name is not given, input file name with
extension`.txt' is used.  If development files for Sqlite3 (package
`libsqlite3-dev') are installed during the build, `gama-local' also
supports reading adjustment input data from an sqlite3 database.  If
run without arguments `gama-local' prints a short help


     $ ./gama-local

     Adjustment of local geodetic network        version: 1.14 / GNU g++
     ************************************
     http://www.gnu.org/software/gama/

     Usage: gama-local  input.xml  [options]
            gama-local  input.xml  --sqlitedb sqlite.db  --configuration name  [options]
            gama-local  --sqlitedb sqlite.db  --configuration name  [options]
            gama-local  --sqlitedb sqlite.db  --readonly-configuration name  [options]

     Options:

     --algorithm  svd | gso | cholesky | envelope
     --language   en | ca | cz | du | es | fi | fr | hu | ru | ua
     --encoding   utf-8 | iso-8859-2 | iso-8859-2-flat | cp-1250 | cp-1251
     --angles     400 | 360
     --latitude   <latitude>
     --ellipsoid  <ellipsoid name>
     --text       adjustment_results.txt
     --xml        adjustment_results.xml
     --cov-band   covariance matrix of adjusted parameters in XML output
                  n  = -1  for full covariance matrix (implicit value)
                  n >=  0  covariances are computed only for bandwidth n
     --version
     --help

Program `gama-local' version is followed by information on compiler
used to build the program (apart from GNU `g++' compiler, two other
possibilities are `bcc' and `msc' for Borland and Microsoft compilers
respectively, when build under Microsoft Windows).

   Option `--algorithm' enables to select numerical method used for
solution of the adjustment. Implicitly is used Singular Value
Decomposition (`svd'), alternatively user can decide for block matrix
algorithm GSO by Frantisek Charamza, based on Gram-Schmidt
orthogonalization. In both these cases, project equations are solved
directly without forming _normal equations_.  Third possibility is to
select Cholesky decomposition of semidefinite matrix of normal
equations (`cholesky').

   Option `--language' selects language used in output protocol. For
example, if run with option `--language cz', `gama-local' prints output
results in Czech languague using UTF-8 encoding. Implicit value is `en'
for output in English.

   Option `--encoding' enables to change inplicit UTF-8 output encoding
to iso-8859-2 (latin-2), iso-8859-2-flat (latin-2 without diacritics),
cp-1250 (MS-EE encoding) cp-12251 (Russian encoding).

   Option `--angles' selects angular units to be used in output.

   Options `--latitude' and/or `--ellipsoid' are used when observed
vertical and/or zenith angles need to be transformed into the
projection plane. If none of these two options is explicitly used, no
corrections are added to horizontal and/or zenith angles. If only one
of these options is used, then implicit value for `--latitude' is 45
degrees (50 gons) and implicit ellipsoid is WGS84.  Mathematical
formulas for the corrections is given in the following section.

   Adjustment results (`--text' and `--xml') can be redirected to
standard output if instead of a file name is used "-" string. If no
output is given, XML adjustment format is implicitly send to standard
output.

   Option `--cov-band' is used to reduce the number of computed
covariances (cofactors) in XML adjustment output. Implicitly full
matrix is written to XML output, which could degrade time efficiency
for the `envelope' algorithm for sparse matrix solution. Explicit
option for full covariance matrix is `--cov-band -1', option
`--cov-band 0' means that only a diagonal of covariance matrix is
written to XML output, `--cov-band 1' results in computing the main
diagonal and first codiagonal etc. If higher rank is specified then
available, it is reduced do maximum possible value `dim-1'.

1.3.1 Reductions of horizontal and zenith angles
------------------------------------------------

For evaluating of reductions of horizontal and zenith angles,
`gama-local' computes a helper point P_1 in the center of the network.
Horizontal and zenith angles observed at point P_2 are transformed to
the projection plane perpendicular to the normal z_1 of the helper
point P_1. Coordinates (x_2, y_2) of point P_2 are conserved, but its
normal z_2 is rotated by the central angle 2\gamma_12 to be parallel
with z_1.

   Formulas for reductions of horizontal and zenith angles are given
only in the printed version.

1.4 Reporting bugs
==================

Undoubtedly there are numerous bugs remaining, both in the C++ source
code and in the documentation.  If you find a bug in either, please
send a bug report to

              bug-gama@gnu.org (mailto:bug-gama@gnu.org)

We will try to be as quick as possible in fixing the bugs and
redistributing the fixes. If you prefere, you can always write directly
to Aleš Čepek (mailto:cepek@gnu.org).

1.5 Contributors
================

The following persons (in chronological order) have made contributions
to GNU Gama project: Aleš Čepek, Jiří Veselý, Petr Doubrava, Jan
Pytel, Chuck Ghilani, Dan Haggman, Mauri Väisänen, John Dedrum, Jim
Sutherland, Zoltan Faludi, Diego Berge, Boris Pihtin, Stéphane
Kaloustian, Siki Zoltan, Anton Horpynich, Claudio Fontana, Bronislav
Koska, Martin Beckett, Jiří Novák, Václav Petráš and Tomáš
Kubín.

   Václav Petráš is the author of *note SQL schema SQLite and
gama-local::.

2 XML input data format for `gama-local'
****************************************

The input data format for a local geodetic network adjustment (program
`gama-local') is defined in accordance with the definition of Extended
Markup Language (XML) for description of structured data.  The XML
definition can be found at

                    `http://www.w3.org/TR/REC-xml'

Input data (points, observations and other related information) are
described using XML start-end pair tags `<xxx>' and `</xxx>' and
empty-element tags `<xxx/>'. The syntax of XML input format is defined
in the Document Type Definition (DTD) at

           `http://www.gnu.org/software/gama/gama-local.dtd'

and can formally be validated independently on the program `gama-local'.

   For parsing the XML input data, `gama-local' uses the XML parser
`Expat' copyrighted by James Clark which is described at

                `http://www.jclark.com/xml/expat.html'

`Expat' is subject to the Mozilla Public License (MPL), or may
alternatively be used under the GNU General Public License (GPL)
instead.

   In the `gama-local' XML input, distances are given in meters,
angular values in centigrades and their standard deviations (rms
errors) in millimeters or centigrade seconds, respectively.
Alternatively angular values in `gama-local' XML input can be given in
degrees and seconds (*note Angular units::).  At the end of this
chapter an example of the `gama-local' XML input data object is given.

2.1 Angular units
=================

Horizontal angles, directions and zenith angles in `gama-local' XML
adjustment input are implicitly given in gons and their standard
deviations and/or variances in centicentigons.  Gon, also called
centesimal grade and Neugrad (German for new grad), is 1/400-th of the
circumference. For example

      <direction  from="202" to="416" val="63.9347"  stdev="10.0" />

The same angular value (direction) can be expressed in degrees as

      <direction  from="202" to="416" val="57-32-28.428"  stdev="3.24" />

In XML adjustment input degrees are coded as a single string, where
degrees (57), minutes (32) and seconds (28.428) are separated by dashes
(-) with optional leading sign. Spaces are not allowed inside the
string. Gons and degrees may be mixed in a single XML document but one
should be careful to supply the information on standard deviations
and/or covariances in the proper corresponding units.

Internally `gama-local' works with gons but output can be transformed
to degrees using the option `--angles 360'.

2.2 Prologue
============

XML documents may, and should, begin with an XML declaration that
specifies the version of XML being used (_prolog_).  In the case of
`gama-local', the XML input data are followed by the XML document type
declaration:

     <?xml version="1.0" ?>
     <!DOCTYPE gama-local
       SYSTEM "http://www.gnu.org/software/gama/gama-local.dtd">

2.3 Tags `<gama-local>' and `<network>'
=======================================

A pair tag `<gama-local>' contains a single pair tag `<network>' that
contains the network definition.  The definition of the network is
composed of three sections:

   * `<description>' of the network (annotation or comments),

   * network `<parameters />' and

   * `<points-observations>' section.

The sections `<description>' and `<parameters />' are optional, the
section `<points-observations>' is mandatory.  These three sections may
be presented in any order and may be repeated several times (in such a
case, the corresponding sections are linked together by the software).

The pair tag `<network>' has two optional attributes `axes-xy' and
`angles'. These attributes are used to describe orientation of the `xy'
orthogonal coordinate system axes and the orientation of the observed
angles and/or directions.

   * `axes-xy="ne"' orientation of axes `x' and `y'; value `ne' implies
     that axis `x' is oriented north and axis `y' is oriented east.
     Acceptable values are `ne', `sw', `es', `wn' for left-handed
     coordinate systems and `en', `nw', `se', `ws' for right-handed
     coordinate systems (default value is `ne').

   * `angles="right-handed"' defines counterclockwise observed angles
     and/or directions, value `left-handed' defines clockwise observed
     angles and/or directions (default value is `left-handed').


Many geodetic systems are right handed with `x' axis oriented east, `y'
axis oriented north and counterclockwise angular observations. Example
of left-handed orthogonal system with different axes orientation is
coordinate system _Krovak_ used in the Czech Republic where the axes
`x' and `y' are oriented south and west respectively.

GNU Gama can adjust any combination of coordinate and angular systems.

Example
=======

     <gama-local>
     <network>
        <description> ... </description>
        <parameters ... />
        <points-observations> ... </points-observations>
     </network>
     </gama-local>

It is planned in future versions of the program to allow more
`<network>' tags (analysis of deformations etc.) and definitions of new
tags.

2.4 Network description
=======================

The description of a geodetic network is enclosed in the start-end pair
tags `<description>'.  Text of the description is copied into the
adjustment output and serves for easier identification of results.  The
text is not interpreted by the program, but it may be helpful for users.

Example
=======

     <description>
     A short description of a geodetic network ...
     </description>

2.5 Network parameters
======================

The network parameters may be listed with the following optional
attributes of an empty-element tag `<parameters />'

   * `sigma-apr = "10"'       value of a priori reference standard
     deviation--square root of reference variance (default value 10)

   * `conf-pr = "0.95"'       confidence probability used in statistical
     tests (dafault value 0.95)

   * `tol-abs = "1000"'       tolerance for identification of gross
     absolute terms in project equations (default value 1000 mm)

   * `sigma-act = "aposteriori"'  actual type of reference standard
     deviation use in statistical tests (`aposteriori | apriori');
     default value is `aposteriori'

   * `update-constrained-coordinates = "no"' enables user to control if
     coordinates of constrained points are updated in iterative
     adjustment. If test on linerarization fails (*note
     Linearization::), Gama tries to improve approximate coordinates of
     adjusted points and repeats the whole adjustment. Coordinates of
     constrained points are implicitly not changed during iterations.

Values of the attributes must be given either in the double-quotes
(`"..."') or in the single quotes (`'...'').  There can be _white
spaces_ (spaces, tabs and new-line characters) between attribute names,
values, and the _equal_ sign.

Example
=======

     <parameters sigma-apr = "15"
                 conf-pr   = '0.90'
                 sigma-act = "apriori"
                 update-constrained-coordinates = "no" />

2.6 Points and observations
===========================

The points and observations section is bounded by the pair tag
`<points-observations>' and contains information about points, observed
horizontal directions, angles, and horizontal distances, height
differences, slope distances, zenith angles, observed vectors and
control coordinates.

Optional attributes of the start tag `<points-observations>' allow for
the definition of default values of standard deviations corresponding
to observed directions, angles, and distances.

   * `direction-stdev = "..."' defines the implicit value of observed
     direction (default value is not defined)

   * `angle-stdev = "..."' defines the implicit value of observed angle
     (default value is not defined)

   * `zenith-angle-stdev = "..."' defines the implicit value of
     observed zenith angle (default value is not defined)

   * `distance-stdev = "..."' defines the implicit value of observed
     horizontal distance (default value is not defined)

Implicit values of standard deviations for the observed distances are
calculated from the model with three constants _a_, _b_, and _c_
according to the formula

                               a + bD^c,

where _a_ is a constant part of the model and _D_ is the observed
distance in kilometres. If the constants _b_ and/or _c_ are not given,
default values _b=0_ and _c=1_ will be used.

Example
=======

     <points-observations direction-stdev = "10"
                          distance-stdev  = "5 3 1" >
        <!-- ... points and observation data ... -->
     </points-observations>

2.7 Points
==========

Points are described by the empty-element tags `<point/>' with the
following attributes:

   * `id = "..."' is the  point identification attribute (mandatory);
     point identification is not limited to _numbers_; all printable
     characters can be used in identification.

   * `x = "..."'    specifies coordinate `x'

   * `y = "..."'    specifies coordinate `y'

   * `z = "..."'    specifies coordinate `z', point height

   * `fix = "..."'  specifies coordinates that are fixed in adjustment;
     acceptable values are `xy', `XY', `z', `Z', `xyz', `XYZ', `xyZ'
     and `XYz'.

   * `adj = "..."'  specifies coordinates to be adjusted (unknown
     parameters in adjustment); acceptable values are `xy', `XY', `z',
     `Z', `xyz', `XYZ', `xyZ' and `XYz'.

With exception of the first attribute (point id), all other attributes
are optional.  Decimal numbers can be used as needed.

Control coordinates marked using the `fix' parameter are not changed in
the adjustment. Uppercase and lowercase notation of coordinates with
the `fix' parameter are interpreted the same.  Corrections are applied
to the unknown parameters identified by coordinates written in
lowercase characters given in the `adj' parameter. When the coordinates
are written using uppercase, they are interpreted as _constrained
coordinates._ If coordinates are marked with both the `fix' and `adj',
the `fix' parameter will take precedence.

_Constrained coordinates_ are used for the regularization of free
networks. If the network is not free (fixed network), the _constrained_
coordinates are interpreted as other unknown parameters.  In classical
free networks, the _constrained_ points define the regularization
constraint

                      \sum dx^2_i+dy^2_i = \min.

where _dx_ and _dy_ are adjusted coordinate corrections and the
summation index _i_ goes over all _constrained_ points.  In other
words, the set of the _constrained_ points defines the adjustment of
the free network (its shape and size) with a simultaneous
transformation to the approximate coordinates of selected points.
Program `gama-local' allows the definition of constrained coordinates
with 1D leveling networks, 2D and 3D local networks.

Example
=======

     <point id="1" y="644498.590" x="1054980.484" fix="xy"  />
     <point id="2" y="643654.101" x="1054933.801" adj="XY" />
     <point id="403" adj="xy" />

2.8 Set of observations
=======================

The pair tag `<obs>' groups together a set of observations which are
somehow related. A typical example is a set of directions and distances
observed from one stand-point. An observation section contains a set of

   * horizontal directions  `<direction ... />'

   * horizontal distances   `<distance ... />'

   * horizontal angles      `<angle ... />'

   * slope distances        `<s-distance ...  />'

   * zenith angles          `<z-angle ... />'

   * height differences     `<dh />'

The band variance-covariance matrix of directions, distances, and angles
listed in one `<obs>' section may be supplied using a `<cov-mat>' pair
tag with attributes `dim' (dimension) and `band' (bandwidth). The
band-width of the diagonal matrix is equal to 0 and a fully-populated
variance-covariance matrix has a bandwidth of `dim-1'.

Observation variances and covariances (i.e. an upper-symmetric part of
the band-matrix) are written row by row between `<cov-mat>' and
`</cov-mat>' tags. If present, the dimension of the variance-covariance
matrix must agree with the number of observations.

The following example of variance-covariance matrix with dimension 6 and
bandwidth 2 (two nonzero codiagonals and three zero codiagonals)

     [ 1.1  0.1  0.2   0    0    0
       0.1  1.2  0.3  0.4   0    0
       0.2  0.3  1.3  0.5  0.6   0
        0   0.4  0.5  1.4  0.7  0.8
        0    0   0.6  0.7  1.5  0.9
        0    0    0   0.8  0.9  1.6 ]

is coded in XML as

     <cov-mat dim="6" band="2">
        1.1  0.1  0.2
             1.2  0.3  0.4
                  1.3  0.5  0.6
                       1.4  0.7  0.8
                            1.5  0.9
                                 1.6
     </cov-mat>

If two or more sets of directions with different orientations are
observed from a stand-point, they must be placed in different `<obs>'
sections. The value of an orientation angle can be explicitly stated
with an attribute `orientation="..."'.  Normally, it is more convenient
to let the program calculate approximate values of orientations needed
for the adjustment. If directions are present, then the attribute
`station' must be defined.

Optional attribute `from_dh="..."' enables to enter implicit height of
instrument for all observations within the `<obs>' pair tag.

Observed distances are expressed in meters, their standard deviations in
millimeters. Observed directions and angles are expressed in centigrades
(400) and their standard deviations in centigrade seconds.

Height differences can be entered in the `<obs>' or
`<height-differences>' section. If entered in the `<obs>' section, the
`dist="..."' parameter is ignored (*note Height differences::).

Example
=======

     <obs from="418">
        <direction  to=  "2" val="0.0000"   stdev="10.0" />
        <direction  to="416" val="63.9347"  stdev="10.0" />
        <direction  to="420" val="336.3190" stdev="10.0" />
        <distance   to="420" val="246.594"  stdev="5.0"  />
     </obs>

     <obs from="418">
        <direction  to=  "2" val="0.0000"   />
        <direction  to="416" val="63.9347"  />
        <direction  to="420" val="336.3190" />
        <distance   to="420" val="246.594"  />

        <cov-mat dim="4" band="0">
           100.00 100.00 100.00 25.00
        </cov-mat>
     </obs>

2.9 Directions
==============

Directions are expressed with the following attributes in an
empty-element tag `<direction />'

   * `to = "..."'      target point identification

   * `val = "..."'     observed direction;  *note Angular units::

   * `stdev = "..."'   standard deviation (optional)

   * `from_dh = "..."' instrument height (optional)

   * `to_dh = "..."'   reflector/target height (optional)


The standard deviation is an optional attribute. However since all
observations in the adjustment must have their weights defined, the
standard deviation must be given either explicitly with the attribute
`stdev="..."' or implicitly with `<points-observation
direction-stdev="..." >' or with a variance-covariance matrix for the
given observation set.  A similar approach applies to all the
observations (distances, angles, etc.)

Example
=======

     <direction  to=  "2" val="0.0000"  stdev="10.0" />
     <direction  to="416" val="63.9347" />

2.10 Horizontal distances
=========================

Distances are written using an empty-element tag `<distance />' with
attributes

   * `from = "..."'    standpoint identification

   * `to = "..."'      target identification

   * `val = "..."'     observed horizontal distance

   * `stdev = "..."'   standard deviation of observed horizontal
     distance (optional)

   * `from_dh = "..."' instrument height (optional)

   * `to_dh = "..."'   reflector/target height (optional)


Contrary to directions,  distances in an observation set (`<obs>') do
not need to share a common stand-point. An example is set of distances
observed from several stand-points with a common variance-covariance
matrix.

Example
=======

     <distance from = "2"  to = "1" val = "659.184" />
     <distance to ="422" val="228.207"  stdev="5.0"  />
     <distance to ="408" val="568.341" />

2.11 Angles
===========

Observed angles are expressed with the following attributes of an
empty-element tag `<angle />'

   * `from = "..."'    standpoint identification (optional)

   * `bs = "..."'      backsight target identification

   * `fs = "..."'      foresight target identification

   * `val = "..."'     observed angle;  *note Angular units::

   * `stdev = "..." '  standard deviation (optional)

   * `from_dh = "..."' instrument height (optional)

   * `bs_dh = "..."'   backsight reflector/target height (optional)

   * `fs_dh = "..."'   foresight reflector/target height (optional)


Similar to distance observations, one observation set may group angles
observed from several standpoints.

Example
=======

     <angle from="433" bs="422" fs="402" val="128.6548" stdev="14.1"/>
     <angle from="433" bs="422" fs="402" val="128.6548" />
     <angle bs="422" fs="402" val="128.6548" stdev="14.1"/>
     <angle bs="422" fs="402" val="128.6548"/>

2.12 Slope distances
====================

Slope distances (space distances) are written using an empty-element tag
`<s-distance />' with attributes

   * `from = "..."'   standpoint identification (optional)

   * `to = "..."'     target identification

   * `val = "..."'    observed slope distance

   * `stdev = "..."'  standard deviation of observed slope distance
     (optional)

   * `from_dh = "..."' instrument height (optional)

   * `to_dh = "..."'   reflector/target height (optional)


Similar to horizontal distances, one observation set may group slope
distances observed from several standpoints.

Example
=======

     <s-distance from = "2"  to = "1" val = "658.824" />
     <s-distance to ="422" val="648.618"  stdev="5.0"  />
     <s-distance to ="408" val="482.578" />

2.13 Zenith angles
==================

Zenith angles are written using an empty-element tag `<z-angle />' with
the following attributes

   * `from = "..."'   standpoint identification (optional)

   * `to = "..."'     target identification

   * `val = "..."'    observed zenith angle; *note Angular units::

   * `stdev = "..."'  standard deviation of observed zenith angle
     (optional)

   * `from_dh = "..."' instrument height (optional)

   * `to_dh = "..."'   reflector/target height (optional)


Similar to horizontal distances, one observation set may group zenith
angles observed from several standpoints.

Example
=======

     <z-angle from = "2"  to = "1" val = "79.6548" />
     <z-angle to ="422" val="85.4890"  stdev="5.0"  />
     <z-angle to ="408" val="95.7319" />

2.14 Height differences
=======================

A set of observed leveling height differences is described using the
start-end tag `<height-differences>' without parameters.  The
`<height-differences>' tag can contain a series of height differences
(at least one) and can optionally be supplied with a
variance-covariance matrix.  Single height differences are defined with
empty tags `<dh />' having the following attributes:
   * `from  = "..."'  standpoint identification

   * `to    = "..."'  target identification

   * `val   = "..."'  observed leveling height difference

   * `stdev = "..."'  standard deviation of levellin elevation and

   * `dist  = "..."'  distance of leveling section (in kilometers)

If the value of standard deviation is not present and length of
leveling section (in kilometres) is defined, the value of standard
deviation is computed from the formula

                         m_dh = m_0 sqrt(D_km)
If the value of standard deviation of the height difference is defined,
information on leveling section length is ignored.  A third possibility
is to define a common variance-covariance matrix for all elevations in
the set.

Example
=======

     <height-differences>
       <dh from="A" to="B" val=" 25.42" dist="18.1" />
       <dh from="B" to="C" val=" 10.34" dist=" 9.4" />
       <dh from="C" to="A" val="-35.20" dist="14.2" />
       <dh from="B" to="D" val="-15.54" dist="17.6" />
       <dh from="D" to="E" val=" 21.32" dist="13.5" />
       <dh from="E" to="C" val="  4.82" dist=" 9.9" />
       <dh from="E" to="A" val="-31.02" dist="13.8" />
       <dh from="C" to="D" val="-26.11" dist="14.0" />
     </height-differences>

2.15 Control coordinates
========================

Control (known) coordinates are described by the start-end pair tag
`<coordinates>'. A series of points with known coordinates can be
defined using the `<point />' tag. The variance-covariance matrix for
the entire set of points can be created with a single `<cov-mat>' tag.
In the `<point />' tags, a point identification (ID) and its
coordinates (x, y and z) must be listed.  Although the order of the
`<point />' tag attributes is irrelevant in the corresponding
variance-covariance matrix, the expected order of the coordinates is x,
y and z (the horizontal coordinates x, y, or the height z might be
missing, but not both). The type of the points may be defined either
directly within the `<coordinates>' tag or outside of it.

Example
=======

     <coordinates>
        <point id="1" x="100.00" y="100.00" />
        <point id="2" z="200.00" y="200.00" x="200.00" />
        <point id="3" z="300.00" />
        <cov-mat dim="6" band="5" >
            ...  <!-- covariances for 1x 1y 2x 2y 2z 3z -->
        </cov-mat>
     </coordinates>

2.16 Coordinate differences (vectors)
=====================================

Observed coordinate differences describe relative positions of station
pairs (vectors). Contrary to the observed coordinates, the
variance-covariance matrix of the coordinate differences always
describes all three elements of the 3D vectors.

Optional attributes of empty element tag `<vec>' for describing
instrument and/or target height are

   * `from_dh = "..."' instrument height

   * `to_dh = "..."'   target height

Example
=======

     <vectors>
        <vec from="id1" to="id2" dx="..." dy="..." dz="..." />
        <vec from="id2" to="id3" dx="..." dy="..." dz="..." />
        ...
        <cov-mat dim="..." band="..." >
            ..
        </cov-mat>
     </vectors>

2.17 Example of local geodetic network
======================================

The XML input data format should be now reasonably clear from the
following sample geodetic network.  This example is taken from user's
guide to Geodet/PC by Frantisek Charamza.

[image: Sketch of the example network]

     <?xml version="1.0" ?>
     <!DOCTYPE gama-local
       SYSTEM "http://www.gnu.org/software/gama/gama-local.dtd">

     <gama-local>
     <network axes-xy="sw">

     <description>
     XML input stream of points and observation data for program Gama
     <!-- this is a XML comment -->
     </description>

     <!-- parameters are expressed with empty-element tag -->

     <parameters sigma-act = "aposteriori" />

     <points-observations>

     <!-- fixed point, constrained point -->

     <point id="1" y="644498.590" x="1054980.484" fix="xy" />
     <point id="2" y="643654.101" x="1054933.801" adj="XY" />

     <!-- computed / adjusted points -->

     <point id="403" adj="xy" />
     <point id="407" adj="xy" />
     <point id="409" adj="xy" />
     <point id="411" adj="xy" />
     <point id="413" adj="xy" />
     <point id="416" adj="xy" />
     <point id="418" adj="xy" />
     <point id="420" adj="xy" />
     <point id="422" adj="xy" />
     <point id="424" adj="xy" />

     <obs from="1">
          <direction  to=  "2" val=  "0.0000" stdev="10.0" />
          <direction  to="422" val= "28.2057" stdev="10.0" />
          <direction  to="424" val= "60.4906" stdev="10.0" />
          <direction  to="403" val="324.3662" stdev="10.0" />
          <direction  to="407" val="382.8182" stdev="10.0" />
          <distance   to=  "2" val= "845.777" stdev="5.0"  />
          <distance   to="422" val= "493.793" stdev="5.0"  />
          <distance   to="424" val= "288.301" stdev="5.0"  />
          <distance   to="403" val= "388.536" stdev="5.0"  />
          <distance   to="407" val= "498.750" stdev="5.0"  />
     </obs>

     <obs from="2">
          <direction  to=  "1" val="0.0000"   stdev="10.0" />
          <direction  to="407" val="22.2376"  stdev="10.0" />
          <direction  to="409" val="73.8984"  stdev="10.0" />
          <direction  to="411" val="134.2090" stdev="10.0" />
          <direction  to="416" val="203.0706" stdev="10.0" />
          <direction  to="418" val="287.2951" stdev="10.0" />
          <direction  to="420" val="345.6928" stdev="10.0" />
          <direction  to="422" val="368.9908" stdev="10.0" />
          <distance   to="407" val="388.562"  stdev="5.0"  />
          <distance   to="409" val="257.498"  stdev="5.0"  />
          <distance   to="411" val="360.282"  stdev="5.0"  />
          <distance   to="416" val="338.919"  stdev="5.0"  />
          <distance   to="418" val="292.094"  stdev="5.0"  />
          <distance   to="420" val="261.408"  stdev="5.0"  />
          <distance   to="422" val="452.249"  stdev="5.0"  />
     </obs>

     <obs from="403">
          <direction  to=  "1" val="0.0000"   stdev="10.0" />
          <direction  to="407" val="313.5542" stdev="10.0" />
          <distance   to="407" val="405.403"  stdev="5.0"  />
     </obs>

     <obs from="407">
          <direction  to=  "1" val="0.0000"   stdev="10.0" />
          <direction  to="403" val="55.1013"  stdev="10.0" />
          <direction  to="409" val="193.3410" stdev="10.0" />
          <direction  to=  "2" val="239.4204" stdev="10.0" />
          <direction  to="422" val="323.5443" stdev="10.0" />
          <distance   to="409" val="281.997"  stdev="5.0"  />
          <distance   to="422" val="346.415"  stdev="5.0"  />
     </obs>

     <obs from="409">
          <direction  to=  "2" val="0.0000"   stdev="10.0" />
          <direction  to="407" val="102.2575" stdev="10.0" />
          <direction  to="411" val="310.1751" stdev="10.0" />
          <distance   to="411" val="296.281"  stdev="5.0" />
     </obs>

     <obs from="411">
          <direction  to=  "2" val="0.0000"   stdev="10.0" />
          <direction  to="409" val="49.8647"  stdev="10.0" />
          <direction  to="413" val="291.4953" stdev="10.0" />
          <direction  to="416" val="337.6667" stdev="10.0" />
          <distance   to="413" val="252.266"  stdev="5.0"  />
          <distance   to="416" val="360.449"  stdev="5.0"  />
     </obs>

     <obs from="413">
          <direction  to="411" val="0.0000"   stdev="10.0" />
          <direction  to="416" val="295.3582" stdev="10.0" />
          <distance   to="416" val="239.745"  stdev="5.0"  />
     </obs>

     <obs from="416">
          <direction  to=  "2" val="0.0000"   stdev="10.0" />
          <direction  to="411" val="68.8065"  stdev="10.0" />
          <direction  to="413" val="117.9922" stdev="10.0" />
          <direction  to="418" val="348.1606" stdev="10.0" />
          <distance   to="418" val="389.397"  stdev="5.0"  />
     </obs>

     <obs from="418">
          <direction  to=  "2" val="0.0000"   stdev="10.0" />
          <direction  to="416" val="63.9347"  stdev="10.0" />
          <direction  to="420" val="336.3190" stdev="10.0" />
          <distance   to="420" val="246.594"  stdev="5.0"  />
     </obs>

     <obs from="420">
          <direction  to=  "2" val="0.0000"   stdev="10.0" />
          <direction  to="418" val="77.9221"  stdev="10.0" />
          <direction  to="422" val="250.1804" stdev="10.0" />
          <distance   to="422" val="228.207"  stdev="5.0"  />
     </obs>

     <obs from="422">
          <direction  to=  "2" val="0.0000"   stdev="10.0" />
          <direction  to="420" val="26.8834"  stdev="10.0" />
          <direction  to="424" val="225.7964" stdev="10.0" />
          <direction  to=  "1" val="259.2124" stdev="10.0" />
          <direction  to="407" val="337.3724" stdev="10.0" />
          <distance   to="424" val="279.405"  stdev="5.0"  />
     </obs>

     <obs from="424">
          <direction  to=  "1" val="0.0000"   stdev="10.0" />
          <direction  to="422" val="134.2955" stdev="10.0" />
     </obs>

     </points-observations>

     </network>
     </gama-local>

3 SQL schema, SQLite and `gama-local'
*************************************

The input data for a local geodetic network adjustment (program
`gama-local') can be strored in SQLite 3 database file.  The general
information about SQLite can be found at

                       `http://www.sqlite.org/'

Input data (points, observations and other related information) are
stored in SQLite database file.  Native SQLite C/C++ API is used for
reading SQLite database file.  It is described at

               `http://www.sqlite.org/c3ref/intro.html'

Please note if you compile GNU Gama as described in *note Install:: and
SQLite library is not installed on your system, GNU Gama would be
compiled without SQLite support.

SQL schema (`CREATE' statements) is in `gama-local-schema.sql' file
which is part of GNU Gama distribution and is in the `xml' directory.

All tables for `gama-local' are prefixed with `gnu_gama_local_'.  In
the documentation table names are referred without this prefix.  For
example table `gnu_gama_local_points' is referred as `points'.

Database scheme used for SQLite database is also valid in other SQL
database systems. Almost every column has some constraint to ensure
correctness.

You can convert existing XML input file to SQL commands with program
`gama-local-xml2sql', for example
     $ gama-local-xml2sql geodet-pc geodet-pc-123.gkf geodet-pc.sql

3.1 Working with SQLite database
================================

First of all you have to create tables for GNU Gama in SQLite database
file (here with `db' extension, but you can choose your own, e.g.
`sqlite').
     $ sqlite3 gama.db < gama-local-schema.sql
You can check created tables by following commands (fist in command
line, second in SQLite command line).
     $ sqlite3 gama.db
     sqlite> .tables
Output should look like this:
     gnu_gama_local_clusters        gnu_gama_local_descriptions
     gnu_gama_local_configurations  gnu_gama_local_obs
     gnu_gama_local_coordinates     gnu_gama_local_points
     gnu_gama_local_covmat          gnu_gama_local_vectors

When you have created tables you can import data.  One way is to
process file with SQL statements.
     $ sqlite3 gama.db < geodet-pc.sql
Another way can be filing database file in another program.

For using `sqlite3' command you need a command line interface for
SQLite 3 installed on your system (e.g. `sqlite3' package).

3.2 Units in SQL tables
=======================

In the `gama-local' SQLite database, distances are given in meters and
their standard deviations (rms errors) in millimeters.  Angular values
are given in radians as well as their standard deviations.

Conversions between radians, gons and degrees:

         rad = gon * pi / 200
         rad = deg * pi / 180
         gon = rad * 200 / pi
         deg = rad * 180 / pi

3.3 Network SQL definition
==========================

Network definitions are stored in the `configurations' table.  This
table contains all parameters for each network such as value of a
priori reference standard deviation or orientation of the `xy'
orthogonal coordinate system axes.

It is obvious that in one database file can be stored more networks
(configurations).

Configuration descriptions (annotation or comments) are stored
separately in table `descriptions'.  The description is split to many
records because of compatibility with various databases (not all
databases implements type `TEXT').

Field (attribute) `conf_id' identifies a configuration in the database.
Field `conf_name' is used to identify configuration outside the database
(e.g. parameter in command-line when reading data from database to
`gama-local').

Table `configurations' contains all parameters specified in tag
`<parameters />' (*note Network parameters::) and also `gama-local'
command line parameters (*note Program gama-local::).  The list of all
table attributes (parameters) follows.

   * `sigma_apr'  value of a priori reference standard deviation--square
     root of reference variance (default value 10)

   * `conf_pr'   confidence probability used in statistical tests
     (dafault value 0.95)

   * `tol_abs'       tolerance for identification of gross absolute
     terms in project equations (default value 1000 mm)

   * `sigma_act'  actual type of reference standard deviation use in
     statistical tests (`aposteriori | apriori'); default value is
     `aposteriori'

   * `update_cc' enables user to control if coordinates of constrained
     points are updated in iterative adjustment. If test on
     linerarization fails (*note Linearization::), Gama tries to
     improve approximate coordinates of adjusted points and repeats the
     whole adjustment. Coordinates of constrained points are implicitly
     not changed during iterations.  Acceptable values are `yes', `no',
     default value is `no'.

   * `axes_xy' orientation of axes `x' and `y'; value `ne' implies that
     axis `x' is oriented north and axis `y' is oriented east.
     Acceptable values are `ne', `sw', `es', `wn' for left-handed
     coordinate systems and `en', `nw', `se', `ws' for right-handed
     coordinate systems (default value is `ne').

   * `angles' `right-handed' defines counterclockwise observed angles
     and/or directions, value `left-handed' defines clockwise observed
     angles and/or directions (default value is `left-handed').

   * `epoch' is measurement epoch.  It is floating point number
     (default value is `0.0').

   * `algorithm' specifies numerical method used for solution of the
     adjustment.  For Singular Value Decomposition set value to `svd'.
     Value `gso' stands for block matrix algorithm GSO by Frantisek
     Charamza based on Gram-Schmidt orthogonalization, value `cholesky'
     for Cholesky decomposition of semidefinite matrix of normal
     equations and value `envelope' for a Cholesky decomposition with
     _envelope_ reduction of the sparse matrix.  Default value is `svd'.

   * `ang_units' Angular units of angles in `gama-local' output.  Value
     `400' stands for gons and value `360' for degrees (default value
     is `400').  Note that this doesn't effect units of angles in
     database.  For further information about angular units see *note
     Angular units::.

   * `latitude' is mean latitude in network area.  Default value is
     `50' (gons).

   * `ellipsoid' is name of ellipsoid (*note Supported ellipsoids::).


All fields are mandatory except `ellipsoid' field.  For additional
information about handling geodetic systems in `gama-local' see *note
Network definition::.

Example (`configuration' table contents):
     conf_id|conf_name|sigma_apr|conf_pr|tol_abs|sigma_act  |update_cc|...
     ---------------------------------------------------------------------
     1      |geodet-pc|10.0     |0.95   |1000.0 |aposteriori|no       |...

     ... axes_xy|angles      |epoch|algorithm|ang_units|latitude|ellipsoid
     ---------------------------------------------------------------------
     ... ne     |left-handed|0.0  |svd      |400      |50.0    |

The list of `description' table attributes follows.
   * `conf_id' is id of configuration which description (text) belongs
     to.

   * `id' identifies text in a database.

   * `text' is part of configuration description.  Its SQL type is
     `VARCHAR(1000)'.


There can be more than one text for one configuration.  All texts
related to one configuration are concatenated to one description.

Example (`description' table contents):
     conf_id|indx|text
     -----------------------------------------------
     1      |1   |Frantisek Charamza: GEODET/PC, ...

3.4 Table `points'
==================

   * `conf_id' is id of configuration which points belongs to.

   * `id' identifies point in a database and also in an output.  It is
     mandatory and it is character string (SQL type is `VARCHAR(80)').
     Point `id' has to be unique within one configuration.  In
     documentation it is referred as point identification or point id.

   * `x', `y' and `z' coordinates of a point.  Coordinate `z' is
     considered as height.

   * `txy' and `tz' specify the type of coordinates `x', `y' and `z'.
     Acceptable values are `fixed', `adjusted' and `constrained' (there
     is no default value).  For details see *note Points::.


Example (table contents):
     conf_id|id |x       |y      |z|txy     |tz
     ------------------------------------------
     1      |201|78594.91|9498.26| |fixed   |
     1      |205|78907.88|7206.65| |fixed   |
     1      |206|76701.57|6633.27| |fixed   |
     1      |207|        |       | |adjusted|

3.5 Table `clusters'
====================

The cluster is a group of observations with the common covariance
matrix.  The covariance matrix allows to express any combination of
correlations among observations in cluster (including uncorrelated
observations, where covariance matrix is diagonal).  For explanation
see *note Observation data and points::.

In the database observations are stored in three tables: `obs',
`coordinates' and `vectors'.  Cluster's covariance matrix is stored in
table `covmat'.  Every observation, vector or coordinate in database
has to be in some cluster.

   * `conf_id' is id of configuration which cluster belongs to.

   * `ccluster' identifies a cluster within one configuration.

   * `dim' and `band' specify dimension and bandwidth of covariance
     matrix.  The bandwidth of the diagonal matrix is equal to 0 and a
     fully-populated covariance matrix has a bandwidth of `dim-1'
     (`band' maximum possible value is `dim-1').

   * `tag' specifies type of observations in cluster which also implies
     the table where they are stored in.  `obs' and
     `height-differences' stand for `obs' table, `coordinates' and
     `vectors' stand for `coordinates' table and `vectors' table
     respectively.


Observations, vectors and coordinates are identified by configuration
id (`conf_id'), cluster id `ccluster' and theirs index (`indx').
Observation index (`indx') has to be unique within observations of one
cluster (which belongs to one configuration).  The same applies for
vectors and coordinates.

See also *note Set of observations::.

Example (table contents):
     conf_id|ccluster|dim|band|tag
     -----------------------------
     1      |1       |3  |0   |obs
     1      |4       |4  |0   |obs

3.6 Table `covmat'
==================

Values of cluster covariance matrix are stored in `covmat' table.
Attributes `conf_id', `ccluster' identifies covariance matrix.  Value
position in matrix is specified by `rind' and `cind' fields.

   * `conf_id' is id of configuration which cluster belongs to.

   * `ccluster' is id of cluster which matrix belongs to.

   * `rind' is row number in covariance matrix

   * `cind' is column number covariance matrix

   * `val' is value itself (variance or covariance).


Values `rind' and `cind' have to respect `dim' and `band' specified in
table `clusters'.  If value in covariance matrix is not specified
(record is missing), it is considered to be zero.  Example (table
contents):
     conf_id|ccluster|rind|cind|val
     --------------------------------
     1      |1       |1   |1   |400.0
     1      |1       |2   |2   |400.0
     1      |1       |3   |3   |400.0
     1      |4       |1   |1   |400.0
     1      |4       |2   |2   |400.0
     1      |4       |3   |3   |400.0
     1      |4       |4   |4   |400.0

3.7 Table `obs'
===============

Table `obs' contains simple observations like direction or distance.

   * `conf_id' is id of configuration which cluster belongs to.

   * `ccluster' is id of cluster which observation belongs to.

   * `indx' identifies observation within cluster.  It has to be
     positive integer.

   * `tag' specifies a type of an observation.  Allowed `tag's follows.

        * `direction' for directions.

        * `distance' for horizontal distances.

        * `angle' for angles.

        * `s-distance' for slope distances (space distances).

        * `z-angle' for zenith angles.

        * `dh' for leveling height differences.


   * `from_id' is stand point identification.  It is mandatory and it
     must not differ within one cluster for observations with `tag =
     'direction'' .

   * `to_id' is target identification (mandatory).

   * `to_id2' is second target identification.  It is valid and
     mandatory only for angles (`tag = 'angle'').

   * `val' is observation value.  It is mandatory for all observation
     types.

   * `stdev' is value of standard deviation.  It is used when variance
     in covariance matrix is not specified.

   * `from_dh' is value of instrument height (optional).

   * `to_dh' is value of reflector/target height (optional).

   * `to_dh2' is value of second reflector/target height (optional).
     It is valid only for angles.

   * `dist' is distance of leveling section. It is valid only for
     height-differences (`tag = 'dh'').

   * `rejected' specifies whether observation is rejected (passive) or
     not.  Value `0' stand for not rejected, value `1' for rejected.
     It is mandatory. Default value is `0'.


Example (table contents without empty columns):
     conf_id|ccluster|indx|tag      |from_id|to_id|val           |rejected
     ---------------------------------------------------------------------
     1      |1       |1   |direction|201    |202  |0.0           |0
     1      |1       |2   |direction|201    |207  |0.817750284544|0
     1      |1       |3   |direction|201    |205  |2.020073921388|0

3.8 Table `coordinates'
=======================

Table `coordinates' contains control (known) coordinates.

   * `conf_id' is id of configuration which cluster belongs to.

   * `ccluster' is id of cluster which coordinates belongs to.

   * `indx' identifies coordinates within cluster.  It has to be
     positive integer.

   * `id' is point identification.

   * `x', `y' and `z' are coordinates.

   * `rejected' specifies whether observation is rejected (passive) or
     not.  Value `0' stand for not rejected, value `1' for rejected.
     Default value is `0'.


See also *note Control coordinates::.

3.9 Table `vectors'
===================

Table `vectors' contains coordinate differences (vectors).

   * `conf_id' is id of configuration which cluster belongs to.

   * `ccluster' is id of cluster which vector belongs to.

   * `indx' identifies vector within cluster.  It has to be positive
     integer.

   * `from_id' is point identification.  It identifies initial point.

   * `to_id' is point identification.  It identifies terminal point.

   * `dx', `dy' and `dz' are coordinate differences.

   * `from_dh' is value of initial point height.  It is optional.

   * `to_dh' is value of terminal point height.  It is optional.

   * `rejected'  integer default 0 not null,


See also *note Coordinate differences::.

3.10 Example of local geodetic network in SQL
=============================================

Providing complete example would be reasonable because of its extent.
However, you can obtain example by following these instructions:

Create a file with XML representation of network by copy and paste
example from *note Example:: to a new file.  Note that file should
start with `<?xml version="1.0" ?>' (no whitespace).  Alternatively you
can use existing XML file from collection of sample networks (see *note
Download::).  Then you can convert your XML file (here
`example_network.xml') to SQL statements by program `gama-local-xml2sql'
(the path depends on your Gama installation).
     $ gama-local-xml2sql example_net example_network.xml example_network.sql
Now you have example network (configuration `example_net') in the form
of SQL `INSERT' statements in the file `example_network.sql'.

Another representations you can create and fill SQLite database (for
details see *note Working with SQLite database::):
     $ sqlite3 examples.db < gama-local-schema.sql
     $ sqlite3 examples.db < example_network.sql
     $ sqlite3 examples.db
Once you have SQLite database, you can work with it from SQLite command
line.  You can get nice output by executing following commands.
     sqlite> .mode column
     sqlite> .nullvalue NULL
     sqlite> SELECT * FROM gnu_gama_local_configurations;
     sqlite> SELECT * FROM gnu_gama_local_points;
     sqlite> SELECT * FROM gnu_gama_local_clusters;
     sqlite> SELECT * FROM gnu_gama_local_covmat;
     sqlite> SELECT * FROM gnu_gama_local_obs;
Or you can get database dump (`CREATE' and `INSERT' statements) by
     sqlite> .dump
If it is not enough for you, you can try one of GUI tools for SQLite.

4 Network adjustment with `gama-local'
**************************************

Adjustment of local geodetic network is a classical case of _adjustment
of indirect observations._  After estimation of approximate values of
unknown parameters (coordinates of points) and linearization of
functions describing relations between observations and parameters we
solve linear system of equations

     (1)      Ax = b + v,

where `A' is coefficient matrix, `b' is vector of absolute terms (right
hand side) and `v' is vector of residuals.  This system is (generally)
overdetermined and we seek the solution `x' satisfying the basic
criterion of Least Squares

     (2)      v'Pv = min,

where `P' is weight matrix. This criterion unambiguously defines the
shape of adjusted network.

In the case of _free network_ the system (1) is singular (matrix `A'
has linearly dependent columns) and we have to define second
regularization criterion

     (3)      \sum x_i^2 = min,      for all selected i

stating that at the same time we demand that the sum of squares
corrections of selected parameters is minimal (corrections of unknown
parameters with indexes from the set of all selected unknowns.
Geometrically this criterion is equivalent to adjustment of the network
according to (2) with simultaneous transformation to the selected set of
fiducial points.  This transformation does not change the shape of
adjusted network.

Often it is advantageous to work with a _homogenized system,_ ie. with
the system of project equations in which coefficient of each row and
absolute term are multiplied by square root of the weight of
corresponding observation.

     (4)      ~A x = ~b,

where ~A = P^{1/2} A, ~b =  P^{1/2} A.  Symbol P^{1/2} denotes diagonal
matrix of square roots of observation weights (or Cholesky
decomposition of covariance matrix in the case of correlated
observations).  To criterion (2) corresponds in the case of homogenized
system criterion

     (5)      ~v'v = min.

Normal equations are clearly equivalent for both systems.

4.1 Approximate coordinates
===========================

For computation of coefficients in system (1) (ie. during
linearization) we need, first of all, an estimate of approximate
coordinates of points and approximate values of orientations of observed
directions sets.

Approximate values of unknown parameters are usually not known and we
have to compute them from the available observations.  For approximate
value of orientation program `gama-local' uses median of all estimates
from the given set of directions to the points with known coordinates.
Median is less sensitive to outliers than arithmetic mean which is
normally used for approximate estimate of orientations

During the phase of computation of approximate coordinate of points,
program `gama-local' walks through the list of computed points and for
each point gathers all determining elements pointing to points with
known or previously computed coordinates.  Determining elements are

     *outer bearing*  (oriented half-line) starting from the point with
     known coordinates and pointing to the computed point

     *distance*       between given and computed points

     *inner angle*    with vertex in the computed point and arms
     intersecting given points


For all combinations of determining elements program `gama-local'
computes intersections and estimates approximate coordinates as the
median of all available solutions.

If at least one point was resolved while iterating through the list,
the whole cycle is repeated.

If no more coordinates can be solved using intersections and points with
unknown coordinates are remaining, program tries to compute coordinates
of unresolved points in a local coordinates system and obtain their
coordinates using similarity transformation. If a transformation
succeeds to resolve coordinates at least one computed point and there
are still some points without coordinates left, the whole process is
repeated.  Classes for computation of approximate coordinates have been
written by Jiri Vesely.

If program `gama-local' fails to compute approximate coordinates of
some of the network points, they are eliminated from the adjustment and
they are listed in the output listing.

With the outlined strategy, program `gama-local' is able to estimate
approximate coordinates in most of the cases we normally meet in
surveying profession. Still there are cases in which the solution fails.
One example is an inserted horizontal traverse with sets of observed
direction on both ends but without a connecting observed distance.  The
solution of approximate coordinates can fail when there is a number of
gross error for example resulting from confusion of point
identifications but in normal situations, leaving computation of
approximate coordinates on program `gama-local' is recommended.

Example
=======

     Computation of approximate coordinates of points
     ************************************************

     Number of points with given coordinates:      2
     Number of solved points                :      2
     Number of observations                 :      4
     -----------------------------------------------------
     Successfully solved points             :      0
     Remaining unsolved points              :      2


     List of unresolved points
     *************************
     422
     424

4.2 Gross absolute terms
========================

One of parameters in XML input of program `gama-local' is tolerance
`tol-abs' for detecting of gross absolute terms in project equations.
Observations with outlying absolute terms are always excluded from
adjustment.

For measured distances program tests difference between observed value
d_i and distance computed from approximate coordinates d_0

              |d_i - d_0| > `tol-abs',

for observed directions program `gama-local' tests transverse deviation
corresponding to absolute term b_i from project equations (1)

              | b_i | d_0 > `tol-abs'

and similarly for angles, program tests the greater of two deviations
corresponding to left and right distances (left and right arm of the
angle)

              |b_i| max{ d_{0_l}, d_{0_r} }  > `tol-abs'.

Default value of parameter `tol-abs' is 1000 mm.

Example
=======

     Outlying absolute terms in project equations
     ********************************************

        i   standpoint       target           observed     absolute
     =========================================== value ===== term ==

        2          103          104 dir.    301.087900       -9989.1


     Observations with outlying absolute terms removed

4.3 Parameters of statistical analysis
======================================

Program `gama-local' uses two basic statistical parameters

   * confidence probability P (default value is 95%, see parameter
     `conf-pr') and

   * actual type of reference standard deviation m0_a (parameter
     `typ-m0').

Confidence probability determines significance level on which
statistical tests of adjusted quatities are carried.  Actual type of
reference standard deviations m0_a specifies whether during statistical
analysis we use a priori reference standard deviation m0 or a
posteriori estimate m0'.

We can choose only the type of actual reference standard deviation (m0
or m0') but not its value. The value corresponds to a priori given
value of reference standard deviation or to the results of adjustment.
On the type of actual reference standard deviation depends the choice
of density functions of stochastic quantities in statistical analysis
of the adjustment.

     *A priori reference standard deviation m0* is used in the cases
     when we know its value in advance and with sufficient reliability.
     Another situation when m0 is used are networks with low number of
     degrees of freedom (poorly overdetermined systems) or when veen
     degrees of freedom is zero. Examples may be analysis of network
     models etc.

     *A posteri estimate of reference standard deviation m0'* is used
     in cases when a priori value of reference standard deviation m0 is
     not known and when degrees of freedom is sufficiently high and
     reliable for empirical estimate of m0'.

The standard deviantion of an adjusted quuantity is computed in
dependence of the choice of actual type of reference standard deviation
m0_a according to formula

                             m0_a sqrt(q)

where q is the weight coefficient of the corresponding adjusted unknown
parameter or observation. Apart from the standard deviation, program
`gama-local' computes for the adjusted quantity its _confidence
interval_ in which its real value is located with the probability P.

4.4 Test on the reference standard deviation
============================================

Null hypothesis H_0: m0 = m0' is tested versus alternative hypothesis
H_1: m0 neq m0'.  Test criterion is ratio of a posteriori estimate of
reference standard deviation

              m0' = sqrt( v'P v / r).

and a priori reference standard deviation m0 (input data parameter
`m0-apr'). For given significance level alpha lower and upper bounds of
interval (L, U) are computed so, that if hypothesis H_0 is true,
probabilities P(m0'/m0 le D) and P(m0'/m0 ge H) are equal to alpha/2.
Lower and upper bounds of the interval are computed as

              L = sqrt((Chi^2_{1-alpha/2,r})/r),
              U = sqrt((Chi^2_{ alpha/2 ,r})/r).

Probability

              P(L < m0'/m0 < U) = `conf-pr'

is by default 95%, this corresponds to 5% confidence level test.

Exceeding the upper limit H of the confidence interval can be caused
even by a single gross error (one outlying observation).  Method of
Least Squares is generally very sensitive to presence of outliers.
Safely can be detected only one observation whose elimination leads to
maximal decrease of a posteriori estimate of reference standard
deviation

     (6)      m0''  = sqrt{(v'P v - delta)/(r-1)},
              delta = max(v_i^2/q_vi),

where

     (7)      q_vi = 1/p_i - q_Li

is weight coefficient of i-th residual.  If the set of observations
contains only one gross error, the outlying observation is likely to be
detected, but this can not be guaranteed.

In addition, program `gama-local' computes a posteriori estimate of
reference standard deviation separately for horizontal distances and
directions and/or angles after formula from

              m0'_t = sqrt(sum{~v^2_it}) / sum{~q_vi}),    t=d,s,

where symbol t denotes observed distances, directions and/or angles.

Example
=======

     m0  apriori  :    10.00
     m0' empirical:     9.64         [pvv] : 3.43560e+03

     During statistical analysis we work

     - with empirical standard deviation 9.64
     - with confidence level             95 %

     Ratio m0' empirical / m0 apriori: 0.964
     95 % interval (0.773, 1.227) contains value m0'/m0
     m0'/m0 (distances): 0.997   m0'/m0 (directions): 0.943

     Maximal decrease of m0''/m0 on elimination of one observation: 0.892

     Maximal studentized residual 2.48 exceeds critical value 1.95
     on significance level 5 % for observation #35
     <distance from="407" to="422" val="346.415" stdev="5.0" />

4.5 Information on points
=========================

Program `gama-local' lists separately review of coordinates of fixed and
adjusted points; adjusted _constrained_ coordinates are marked with
`*'; see equation (3).  Adjusted coordinate standard deviations m_x and
m_y, and values for computing confidence intervals are given in the
listing of adjusted coordinates (*note Statistical analysis::).  In the
review index i is the index of unknown x_i from the system of project
equations (1) corresponding to the point coordinates x and y.

Example
=======

     Fixed points
     ************

            point         x              y
     ========================================

                1  1054980.484     644498.590
                2  1054933.801     643654.101


     Adjusted coordinates
     ********************

       i        point    approximate  correction  adjusted    std.dev conf.i.
     ====================== value ====== [m] ====== value ========== [mm] ===

                  422
       2            x   1055167.22747  -0.00510 1055167.22237     2.7     5.4
       3            y    644041.46119   0.00023  644041.46142     2.5     5.1

                  424
       4            X * 1055205.41198  -0.00056 1055205.41142     3.1     6.3
       5            Y *  644318.24425  -0.00125  644318.24300     3.6     7.2

For adjusted points, program summarizes information on standard
ellipses, confidence ellipses, mean square positional errors (m_p),
mean coordinate errors (m_xy) and coefficients g characterizing
position of approximate coordinates with regard to the confidence
ellipse.

Example
=======

     Mean errors and parameters of error ellipses
     ********************************************

       point     mp      mxy      mean error ellipse  conf.err. ellipse   g
     ========== [mm] == [mm] ==== a [mm] b  alpha[g] ==== a' [mm] b' ========

         422     3.6     2.6     2.7     2.5   187.0     6.8     6.4     0.8
         424     4.7     3.4     3.7     2.9   131.8     9.5     7.4     0.2
         403     5.7     4.0     4.3     3.6    78.9    11.0     9.3     1.1

Mean square positional error m_p and mean coordinate error (m_xy) are
computed as

              m_p = sqrt(m_y^2 + m_x^2),    m_xy = m_p / sqrt(2),

where m_y^2 and m_x^2 are squares of standard deviations (variances) of
adjusted points coordinates.

Semimajor and semiminor axes of standard ellipse are denoted as a and b
in the listing, bearing of semimajor axis is denoted as alpha and they
are computed from covariances of adjusted coordinates

              a = sqrt(1/2(cov_yy + cov_xx + c),
              b = sqrt(1/2(cov_yy + cov_xx - c),

              c = sqrt( (cov_xx - cov_yy)^2 + 4(cov_xy)^2 ),

              tan 2alpha = 2(cov_xy) / (cov_xx - cov_yy).

The angle alpha (the bearing of semimajor axis) is measured clockwise
from X axis.

Probability that standard ellipse covers real position of a point is
relatively low. For this reason program `gama-local' computes extra
_confidence ellipse_ for which the probability of covering real point
position is equal to the given confidence probability.  Both ellipsy
are located in the same center, they share the same bearing of
semimajor axes and they are similar.  For lengths of their semi-axis
holds

              a' = k_p a,        b' = k_p b,

where k_p is a coefficient computed for the given probability P as
defined in *note Statistical analysis::.

[image: Approximate position of adjusted point with
        regard to confidence ellipse]

Position of  approximate coordinates of an adjusted point with respect
to its confidence ellipse are expressed by a coeeficient g Three cases
are possible

     g < 1 approximate coordinates of adjusted point are located inside
     the confidence ellipse

     g = 1 approximate coordinates of adjusted point are located on the
     confidence ellipse

     g > 1 approximate coordinates of adjusted point are outside the
     confidence ellipse

The coefficient g is calculated from formula

              g = sqrt( (a_0 / a')^2 + (b_0/b')^2 )

where

              b_0 = delta_y cos(alpha) - delta_x sin(alpha),
              a_0 = delta_y sin(alpha) - delta_x cos(alpha)

symbol delta is used for correction of approximate coordinates and
alpha is bearing of confidence ellipse semimajor axis.

If network contains sets of observed directions, program writes
information on corresponding adjusted orientations, standard deviations
and confidence intervals.  Index i is the same as in the case of
adjusted coordinates the index of i-th adjusted unknown in the project
equations.

Example
=======

     Adjusted bearings
     *****************

       i   standpoint   approximate  correction  adjusted   std.dev conf.i.
     ==================== value [g] ==== [g] === value [g] ======= [cc] ===

       1            1    296.484371  -0.000917  296.483454      5.1    10.3
      10            2     96.484371   0.000708   96.485079      5.1    10.4
      21          403     20.850571  -0.001953   20.848618      8.8    17.7

4.6 Adjusted observations and residuals
=======================================

In the review of adjusted observations program `gama-local' prints
index of the observation, index of the row in matrix `A' in the system
(1), identifications of standpoint and target point, type of the
observation, its approximate and adjusted value, standard deviation and
confidence interval.

Example
=======

     Adjusted observations
     *********************

        i   standpoint   target         observed     adjusted std.dev conf.i.
     ===================================== value ==== [m|g] ====== [mm|cc] ==

        1            1        2 dis.   845.77700    845.77907     3.0     6.1
        2                   422 dir.   28.205700    28.205613     5.1    10.3
        3                   424 dir.   60.490600    60.491359     6.7    13.6

Review of residuals serves for analysis of observations and containts
values of normalized or studentized residuals (depending on type of
m0_a used) and three characteristics.  Theese are coefficient `f'
identifying weak network elements and estimates of real error of
observation `e-obs' and real error of its adjusted value `e-adj', see
definition in the following text.

If normalized or studentized residual exceeds critical value for the
given confidence probability, it is marked in the review with symbol
`c' (critical) and maximal normalized or studentized residual is marked
with symbol `m'.

Example
=======

     Residuals and analysis of observations
     **************************************

        i standpoint   target        f[%]        v    |v'|     e-obs.  e-adj.
     ======================================== [mm|cc] =========== [mm|cc] ===

        1          1        2 dir.   47.4       9.170  1.1      12.7    3.5
        2                 422 dir.   47.0      -0.873  0.1      -1.2   -0.3
        3                 424 dir.   30.3       7.588  1.1      14.8    7.2

4.7 Identification of weak network elements
===========================================

When planning observations in a geodetic network we always try to
guarantee that all observed elements are checked by other measurements.
Only with redundant measurements it is possible to adjust observations
and possibly remove blunders that might otherwise totaly corrupt the
whole set of measurements. Apart from sufficient number of redundant
observations the degree of control of single observed elements is given
by the network configuration, ie. its geometry.

Less controlled observations represent weak network elements and they
can in extreme cases even disable detection of gross observational
errors as it is in the case of uncontrolled observations.  There are
two limit cases of observation control

     *fully controlled observation* as is for example an observed
     distance between two fixed points (standard deviation of the
     adjusted element is zero; standard deviation of the residual
     equals to the standard deviation if the observation) and

     *uncontrolled observations* as is a free polar bar for example
     (standard deviation of adjusted value is equal to standard
     deviation of observed quantity; residual and standard deviation of
     the residual are zero).

Weakly controlled or uncontrolled observations can result even from
elimination of certain suspisios observations during analysis of
adjusment.

Standard deviation of adjusted observations is less than standard
deviation of the measurement.  Degree of observation control in network
is defined as coefficient

     (8)      f = 100 (m_l - m_L)/m_l,

where m_l is standard deviation of observed quantity and m_L is standard
deviation computed from a posteriori reference standard deviation m0.
We consider observed network element to be

     *uncontrolled* if f < 0.1 (in listing marked with letter `u'),

     *weakly controlled* if 0.1 le f < 5 (in listing marked with letter
     `w').

4.8 Estimation of real errors
=============================

Acording to previous section we can consider an observation to be
controlled if its coefficient f > 0.1.  Any controlled observation can
be eliminated from the network without corrupting the network
consistency--network reduced by one controlled observation can be
adjusted and all unknown parameters can be compute without the
eliminated observation.

Estimate of real error of i-th observation is defined as

     (9)      e_li = L^red_i - l_i,

where e_li is value of i-th observation and is value of i-th network
element computed from adjusted coordinates and/or orientations of the
reduced network.  Similarly is defined the estimate of real error of a
residual

     (10)     e_vi = L^red_i - L_l.

Adjustment results are the best statistical estimate of unknown
parameters that we have. This holds true even for adjustment of
_reduced_ network which is not influenced by real error of i-th
observation.  On favourable occasions differences (9) and (10) can help
to detect blunders but to interpret these estimates as _real errors_ is
possible only with substantial exaggeration.  These estimates fail when
there are more than one significant observational error. Generally
holds tha the weaker the element is controlled in netowrk the less
reliable these estimates are.

Estimate of real error of an observation computes program `gama-local'
as

              e_li = v_i/(p_i q_vi)

and estimate of real error of a residual as

              e_vi = e_li - v_i.

4.9 Test on linearization
=========================

Mathematical model of geodetic network adjustment in `gama-local' is
defined as a set of known real-valued differentiable functions

     (11)      L^* = f(X^*)

where L^* is a vector of theoretical correct observations and X^* is a
vector of correct values of parameters. For the given sample set of
observations `L' and the unknown vector of residuals `v' we can express
the estimate of parameters `X' as a nonlinear set of equations

     (12)      L + v = f(X).

With approximate values `X_0' of unknown parameters

     (12)      X = X_0 + x

we can linearize the equations (12)

               L + v = f(X_0) + f'(X_0)x.

yielding the linear set of equations (1)

Unknown parameters in `gama-local' mathematical model are points
coordinates and orientation angles (transforming observed directions to
bearings). The observables described by functions (12) belong into two
classes

     *linear observables*: horizontal and slope distances, height
     differences, control coordinates and vectors (coordinate
     differences),

     *angular observables*: directions, horizontal and zenith angles.

Internally in `gama-local' unknown corrections to linear observables
are computed in millimeters and corrections to angular observables in
centigrade seconds. To reflect the internal units in used all partial
derivatives of angular observables by coordinates are scaled by factor
2000/pi.

When computing coefficients of project equations (1) we expect that
approximate coordinates of points are known with sufficient accuracy
needed for linearization of generally nonlinear relations between
observations and unknown paramters. Most often this is true but not
always and generally we have to check how close our approximation is to
adjusted parameters.

Generally we check linearization in adjustment by double calculation of
residuals

              v^I  = Ax - b,
              v^II = ~l(~x) - l,


Program `gama-local' similarly computes and tests differences in values
of adjusted observations once computed from residuals and once from
adjusted coordinates. For measured directions and angles `gama-local'
computes in addition transverse deviation corresponding to computed
angle difference in the distance of target point (or the farther of two
targets for angle).  As a criterion of bad linearization is supposed
positional deviation greater or equal to 0.0005 millimetres.

Example
=======

     Test of linearization error
     ***************************

     Diffs in adj. obs from residuals and from adjusted coordinates
     **************************************************************

      i standpoint     target          observed     r        difference
     =================================   value  = [mm|cc] = [cc] == [mm]=

      2 3022184030 3022724008 dist.   28.39200    -7.070          -0.003
      3            3022724002 dist.   72.30700   -18.815          -0.001
      7            3000001063 dir.  286.305200    11.272  -0.002  -0.001
      8            3022724008 dir.  357.800600   -23.947   0.037   0.002

From the practical point of view it might seem that the tolerance
0.0005 mm for detecting poor linearization is too strict.  Its
exceeding in program `gama-local' results in repeated adjustment with
substitute adjusted coordinates for approximate. Given tolerance was
chosen so strict to guarantee that listed output results would never be
influenced by linearization and could serve for verification and
testing of numerical solutions produced by other programs.

Implicitly coordinates of constrained points are not changed in
iterative adjustments. This feature can be changed in XML input data by
setting `<parameters update-constrained-coordinates = "yes" />' (*note
Network parameters::).

Iterated adjustement with successive improvement of approximate
coordinates converges usually even for gross errors in initial estimates
of unknown coordinates. If the influence of linearization is detected
after adjustment, quite often only one iteration is sufficient for
recovering.

For any automatically controlled iteration we have to set up certain
stopping criterion independent on the convergence and results obtained.
Program `gama-local' computes iterated adjustment three times at
maximum.  If the bad linearization is detected even after three
readjustments it signals that given network configuration is somehow
suspicious.

5 Data structures and algorithms
********************************

5.1 Observation data and points
===============================

The Gama observation data structures are designed to enable adjustment
of any combination of possibly correlated observations.  At its very
early stage Gama was limited to adjustment of uncorrelated
observations. Only directions and distances were available and
observable's weight was stored together with the observed value in a
single object. A single array of pointers to observation objects was
sufficient for handling all observations. So called _orientation
shifts_ corresponding to directions measured form a point were stored
together with coordinations in _point objects_.

[image: Schema of observation data structures]

To enable adjustment of possibly correlated observations (like angles
derived from observed directions or already adjusted coordinates from a
previous adjustment) Gama has come with the concept of _clusters_.
Cluster is an object with a common variance-covariance matrix and a
list of pointers to observation objects (distances, directions, angles,
etc.). Weights were removed from observation objects and replaced with
a pointer to the cluster to which the observation belong. All clusters
are joined in a common object `ObservationData'; similarly to
observations, each cluster contains a pointer to its parent
`Observation Data' object.  _Orientation shifts_ were separated from
coordinates and are stored in the cluster containing the bunch of
directions and thus number of orientations is not limited to one for a
point.

This organisation of observational information has proved to be
effective.  Template classes `ObservationData' and `Cluster' are used
as base classes both in `gama-local' and `gama-g3'

template <typename Observation>
  class ObservationData
  {
  public:
    ClusterList<Observation>  CL;

    ObservationData();
    ObservationData(const ObservationData& cod);
    ~ObservationData();

    ObservationData& operator=(const ObservationData& cod);
    template <typename P> void for_each(const P& p) const;
  };

template <typename Observation>
  class Cluster
  {
  public:
    const ObservationData<Observation>*     observation_data;
    ObservationList<Observation>            observation_list;
    typename Observation::CovarianceMatrix  covariance_matrix;

    Cluster(const ObservationData<Observation>* od);
    virtual ~Cluster();

    virtual Cluster* clone(const ObservationData<Observation>*) const = 0;
    double stdDev(int i) const;
    int size() const;
    void update();
    int  activeCount() const;
    typename Observation::CovarianceMatrix activeCov() const;
  };

The following template class `PointBase' for handling point information
is used in `gama-g3'. The template class `PointBase' relies internally
on `std::map' container but comes with its own interface (in
`gama-local' `std::map' was used directly for storing points).

template <typename Point>
  class PointBase
  {
    typedef std::map<typename Point::Name, Point*>  Points;

  public:
    PointBase();
    PointBase(const PointBase& cod);
    ~PointBase();

    PointBase& operator=(const PointBase& cod);
    void put(const Point&);
    void put(Point*);
    Point*       find(const typename Point::Name&);
    const Point* find(const typename Point::Name&) const;
    void erase(const typename Point::Name&);
    void erase();

    class const_iterator;
    const_iterator  begin();
    const_iterator  end  ();

    class iterator;
    iterator  begin();
    iterator  end  ();
  };

Template classes `ObservationData' and `PointBase' are defined in
namespace `GNU_gama' and are located in the source directory `gnu_gama'.

5.2 Supported ellipsoids
========================

id             a              b, 1/f, f      description            
airy           6377563.396    6356256.910    Airy ellipsoid 1830    [4]
airy_mod       6377340.189    6356034.446    Modified Airy          [4]
apl1965        6378137        298.25         Appl. Physics. 1965    [4]
andrae1876     6377104.43     300.0          Andrae 1876 (Denmark,  [4]
                                             Iceland)               
australian     6378160        298.25         Australian National    [3]
                                             1965                   
bessel         6377397.15508  6356078.96290  Bessel ellipsoid 1841  [1]
bessel_nam     6377483.865    299.1528128    Bessel 1841 (Namibia)  [4]
clarke1858a    6378361        6356685        Clarke ellipsoid 1858  [3]
                                             1st                    
clarke1858b    6378558        6355810        Clarke ellipsoid 1858  [3]
                                             2nd                    
clarke1866     6378206.4      6356583.8      Clarke ellipsoid 1866  [3]
clarke1880     6378316        6356582        Clarke ellipsoid 1880  [3]
clarke1880m    6378249.145    293.4663       Clarke ellipsoid 1880  [4]
                                             (modified)             
cpm1799        6375738.7      334.29         Comm. des Poids et     [4]
                                             Mesures 1799           
delambre       6376428        311.5          Delambre 1810          [4]
                                             (Belgium)              
engelis        6378136.05     298.2566       Engelis 1985           [4]
everest1830    6377276.345    300.8017       Everest 1830           [4]
everest1848    6377304.063    300.8017       Everest 1948           [4]
everest1856    6377301.243    300.8017       Everest 1956           [4]
everest1869    6377295.664    300.8017       Everest 1969           [4]
everest_ss     6377298.556    300.8017       Everest (Sabah and     [4]
                                             Sarawak)               
fisher1960     6378166        298.3          Fisher 1960 (Mercury   [3] [4]
                                             Datum)                 
fisher1960m    6378155        298.3          Modified Fisher 1960   [3] [4]
fischer1968    6378150        298.3          Fischer 1968           [4]
grs67          6378160        298.2471674270 GRS 67 (IUGG 1967)     [4]
grs80          6378137        298.257222101  Geodetic Reference     [1]
                                             System 1980            
hayford        6378388        297            Hayford 1909           [1] [3]
                                             (International)        
helmert        6378200        298.3          Helmert ellipsoid      [3]
                                             1906                   
hough          6378270        297            Hough                  [4]
iau76          6378140        298.257        IAU 1976               [4]
international  6378388        297            International 1924     [1] [3]
                                             (Hayford 1909)         
kaula          6378163        298.24         Kaula 1961             [4]
krassovski     6378245        298.3          Krassovski ellipsoid   [1]
                                             1940                   
lerch          6378139        298.257        Lerch 1979             [4]
mprts          6397300        191.0          Maupertius 1738        [4]
mercury        6378166        298.3          Mercury spheroid 1960  [3]
merit          6378137        298.257        MERIT 1983             [4]
new_intl       6378157.5      6356772.2      New International      [4]
                                             1967                   
nwl1965        6378145        298.25         Naval Weapons Lab.,    [4]
                                             1965                   
plessis        6376523        6355863        Plessis 1817 (France)  [4]
se_asia        6378155        6356773.3205   Southeast Asia         [4]
sgs85          6378136        298.257        Soviet Geodetic        [4]
                                             System 85              
schott         6378157        304.5          Schott 1900 spheroid   [3]
sa1969         6378160        298.25         South American         [3]
                                             Spheroid 1969          
walbeck        6376896        6355834.8467   Walbeck                [4]
wgs60          6378165        298.3          WGS 60                 [4]
wgs66          6378145        298.25         WGS 66                 [4]
wgs72          6378135        298.26         WGS 72                 [4]
wgs84          6378137        298.257223563  World Geodetic System  [1]
                                             1984                   

[1]   Milos Cimbalnik - Leos Mervart: Vyssi geodezie 1, 1997,
      Vydavatelstvi CVUT, Praha
[2]   Milos Cimbalnik: Derived Geometrical Constants of the Geodetic
      Reference System 1980, Studia geoph. et geod. 35 (1991), pp.
      133-144, NCSAV, Praha
[3]   Glossary of the Mapping Sciences, Prepared by a Joint Committe of
      the American Society of Civil Engineers, American Congress on
      Surveying and Mapping and American Society for Photogrammetry and
      Remote Sensing (1994), USA, ISBN 1-57083-011-8, ISBN 0-7844-0050-4
[4]   Gerald Evenden: proj - forward cartographic projection filter
      (rel. 4.3.3), http://www.remotesensing.org/proj

5.3 Transformation from spatial to geographical coordinates
===========================================================

Spatial coordinates (X, Y, Z) can be easily computed from geographical
ellipsoidal coordinates (B, L, H), where B is geographical latitude, L
geographical longitude and H is elliposidal height, as

     X = (N + H) cos B cos L
     Y = (N + H) cos B sin L
     Z = (N(1-e^2) + H)sin B

where N = a/sqrt(1 - e^2 sin^2 B) is the radius of curvature in the
prime vertical, e^2 = (a^2 - b^2)/a^2 is the first eccentricity for the
given rotational ellipsoid (spheroid) with semi-major axis a and
semi-minor axis b.

In the case of coordiante transformation from (X, Y, Z) to (B, L, H),
the longitude is given by the formula

     tan L = Y / X.

Now we can introduce

     D = sqrt(X^2 + Y^2),

so that the cartesian system become (D, Z).  Coordinates B and H are
then usually computed by iteration with some starting value of B_0, for
example

     tan B_0 = Z/D/(1 - e^2),

     tan B = Z/D + N/(N+H) e^2 tan B,   H  = D / cos B = Z / sin B - N(1-e^2)

B. R. Bowring described a closed formula(1) that is more effective and
sufficiantly accurate and that is used in GNU Gama.

[image: Spatial and geographical coordinates]

The centre of curvature C of the spheroid corresponding to P' is the
point

                  (e^2 a cos^3 u,  -e'^2 b sin^3 u)),

where e'^2 = (a^2 - b^2)/b^2 is second eccentricity and u is the
parametric latitude of the point P',  (1-e^2)N sin B = b sin u.
Therefore

          tan B = (Z + e'^2 b sin^3 u) / (D - e^2 a cos^3 u).
This is clearly an iterative solution; but it has been found that this
formula is extremely accurate using the single first approximation for
u for the tan u = (Z/D)(a/b).  Maximum error in earth bound region is
3e-8 of sexadecimal arc seconds (5e-7 millimetres); maximum is 0.0018"
(0.1 millimetres) at height H = 2a.

---------- Footnotes ----------

(1) B. R. Bowring: Transformation from spatial to geographical
coordinates, Survey Review XXIII, 181, July 1976

5.4 Class `g3::Model'
=====================

g3::model documentation shall come here ...

namespace GNU_gama {  namespace g3 {


  class Model {
  public:

    typedef GNU_gama::PointBase<g3::Point>              PointBase;
    typedef GNU_gama::ObservationData<g3::Observation>  ObservationData;

    PointBase           *points;
    ObservationData     *obs;

    GNU_gama::Ellipsoid  ellipsoid;


    Model();
    ~Model();

    Point* get_point(const Point::Name&);
    void   write_xml(std::ostream& out) const;
    void   pre_linearization();
}}

Appendix A Copying This Manual
******************************

A.1 GNU Free Documentation License
==================================

                        Version 1.1, March 2000

     Copyright (C) 2000 Free Software Foundation, Inc.
     51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA

     Everyone is permitted to copy and distribute verbatim copies
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  0. PREAMBLE

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     We have designed this License in order to use it for manuals for
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       Copyright (C)  YEAR  YOUR NAME.
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Concept Index
*************

<angle />:                                     See 2.11.     (line  786)
<coordinates>:                                 See 2.15.     (line  923)
<description>:                                 See 2.4.      (line  476)
<direction />:                                 See 2.9.      (line  723)
<distance />:                                  See 2.10.     (line  754)
<gama-local>:                                  See 2.3.      (line  419)
<height-differences>:                          See 2.14.     (line  880)
<network>:                                     See 2.3.      (line  419)
<obs>:                                         See 2.8.      (line  632)
<parameters />:                                See 2.5.      (line  491)
<point />:                                     See 2.7.      (line  573)
<points-observations>:                         See 2.6.      (line  530)
<s-distance />:                                See 2.12.     (line  820)
<vectors>:                                     See 2.16.     (line  950)
<z-angle />:                                   See 2.13.     (line  850)
absolute terms:                                See 4.2.      (line 1697)
analysis, statistical:                         See 4.3.      (line 1737)
angle:                                         See 2.11.     (line  786)
angle, zenith:                                 See 2.13.     (line  850)
contributors:                                  See 1.5.      (line  333)
coordinate differences:                        See 2.16.     (line  950)
coordinates, observed:                         See 2.15.     (line  923)
description, network:                          See 2.4.      (line  476)
deviation, reference standard:                 See 4.4.      (line 1784)
deviation, standard:                           See 4.4.      (line 1784)
difference, height:                            See 2.14.     (line  880)
direction:                                     See 2.9.      (line  723)
distance, horizontal:                          See 2.10.     (line  754)
distance, slope:                               See 2.12.     (line  820)
download:                                      See 1.1.      (line  142)
FDL, GNU Free Documentation License:           See A.1.      (line 2511)
gama-local:                                    See 1.3.      (line  211)
gross absolute terms:                          See 4.2.      (line 1697)
height differences:                            See 2.14.     (line  880)
height, difference:                            See 2.14.     (line  880)
horizontal distance:                           See 2.10.     (line  754)
horizontal, distance:                          See 2.10.     (line  754)
information on points:                         See 4.5.      (line 1855)
install:                                       See 1.2.      (line  160)
network description:                           See 2.4.      (line  476)
network parameters:                            See 2.5.      (line  491)
observations, Points:                          See 2.6.      (line  530)
observations, set:                             See 2.8.      (line  632)
observed coordinates:                          See 2.15.     (line  923)
observed, coordinates:                         See 2.15.     (line  923)
parameters of statistical analysis:            See 4.3.      (line 1737)
parameters, network:                           See 2.5.      (line  491)
point:                                         See 2.7.      (line  573)
points:                                        See 4.5.      (line 1855)
points and observations:                       See 2.6.      (line  530)
points, observations:                          See 2.6.      (line  530)
prologue:                                      See 2.2.      (line  407)
reductions, horizontal and zenith angles:      See 1.3.1.    (line  306)
reference standard deviation:                  See 4.4.      (line 1784)
Reporting bugs:                                See 1.4.      (line  320)
set of observations:                           See 2.8.      (line  632)
set, observations:                             See 2.8.      (line  632)
slope distance:                                See 2.12.     (line  820)
slope, distance:                               See 2.12.     (line  820)
standard deviation:                            See 4.4.      (line 1784)
statistical analysis:                          See 4.3.      (line 1737)
terms, absolute:                               See 4.2.      (line 1697)
test on the reference standard deviation:      See 4.4.      (line 1784)
vector:                                        See 2.16.     (line  950)
zenith angle:                                  See 2.13.     (line  850)
zenith, angle:                                 See 2.13.     (line  850)