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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
<direction … />
<distance … />
<angle … />
<s-distance … />
<z-angle … />
<azimuth … />
The band variance-covariance matrix of directions, distances, angles
or other observations
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 (Height differences).
<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> |
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This document was generated by Ales Cepek on September 16, 2017 using texi2html 1.82.