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## 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

  

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