3. COR File

The .cor file contains the initial values of points coordinates and their constraints.

All points may be declared or only the minimum amount for allowing automatic Parameters Initialization to compute the coordinates of all the other points. In the case of a simulation project, it is mandatory to declare the coordinates of all points, as the observations values are not taken into account.

For example in case of a 3D computation, in order to settle the project translation, it is necessary to constrain at least an X, a Y and a Z coordinates, not necessarily on the same point. These constaints must appear in the .cor file.

3.1. Protocol for .COR File

The coordinates file is a plain text file with .cor as an extension. It has one line per point, containing the following fields:

\(code\ name\ E\ N\ h\ [\sigma_E\ \sigma_N\ \sigma_h\ [\eta\ \xi]]\ [*comment]\)

  • code: point dimension and type of contraints

    • 0: 3D free point

    • 1: 3D point constrained on ENh

    • 2: 3D point constrained on EN

    • 3: 3D point constrained on h

    • 4: 1D free point

    • 5: 1D point constrained on h

    • 6: 2D free point

    • 7: 2D point constrained on EN

    • 8: remote 2D free point, excluded from internal constraints

    • 9: remote 2D point constrained on EN, excluded from internal constraints

    • -1: point to be ignored in .obs and not used in computation, useful for project debugging

  • name: point name

  • E, N: Easting and Northing coordinates in input projection of the project

  • h: ellipsoidal height or altitude (see Reference Frame in .COR File)

  • \(\sigma_E,\ \sigma_N,\ \sigma_h\): a priori precisions of constraints

  • \(\eta,\ \xi\): Easting and Northing vertical deflection, in arcseconds

  • comment: saved and displayed in the report

Note

\(\sigma_E\), \(\sigma_N\) and \(\sigma_h\) are mandatory only in case of constrained points or when \(\eta\) and \(\xi\) are expected.

A negative value for \(\sigma\) deactivates the corresponding constraint.

If \(\sigma\) on a constrained coordinate is set to 0, the corresponding parameter is removed from the computation (the coordinate is fixed).

Note

\(\eta\) and \(\xi\) are mandatory on every verticalized point in order to use vertical deflection in computation.

Note

For ignored points (code -1), only the code and the point name are mandatory.

Note

.cor subfiles can be included into a .cor file using @ (see Example of .COR File).

3.2. Reference Frame in .COR File

Coordinates in a .cor file are provided in a local stereographic projection, in meters or using any projection, as defined in Project Configuration.

The vertical component must be close to the ellipsoidal height, except in case of leveling (1D) compensation where altitude can be used (see Project Configuration).

Note

The a priori precisions are always given in the internal computation frame (see Spherical Coordinates), that has no scale error or convergence of meridians.

3.3. 1D Points

In the case of 1D points (code 4 or 5), all coordinates are mandatory. The altimetric component will be the only parameter for least squares, but the planimetric coordinates are used to compute the precision of the observation, if it has a part relative to distance, and the correction of the vertical deviation.

The planimetric coordinates are also used to correctly display the points on the report map.

3.4. 2D Points

In the case of 2D points (code 6 to 9), all coordinates are mandatory, the vertical coordinate is used only as information and for precision computation.

Remote 2D points (code 8 and 9) are the same as normal 2D points except that they are not used for internal constraints (see Internal Constraints).

3.5. Example of .COR File

 1  S1 100.000  100.000  50.000 0.0010 0.0010 0.0010   *3d constr
 2  S3  82.961  103.782  50.074 0.0100 0.0100 0.0000   *plani constr
 0  S2  89.930  100.827  50.067                        *free
 3  S4  76.453  100.878  50.034 0.0000 0.0000 0.0001   *alti constr
 0  S5  64.648  100.000  49.921 0.0000 0.0000 0.0000
 0  S6  54.648  110.000  38.451 0.0000 0.0000 0.0000 0.0003 0.0002 *vert deflection
 1  S7  64.648  100.000  49.921 0.0001 0.0001 0.0010
 1  S8  64.648  100.000  49.921 0      0      0        *fixed point
 1  S9 100.000  100.000  50.000 -0.0010 0.0010 0.0010  *N and h constr
-1  S10                                                *ignored point
 @detail.cor * subfile

Each constraint on the coordinates of a point with \(\sigma>0\) adds an observation in the bundle adjustment computation.

3.6. Point Class

In the graphical user interface and report, the point class is displayed in an abbreviated form in order to easily see its dimensions and constraints. A - indicates a dimension without constraint, the name of the coordinate in lowercase letter when the coordinate is constrained and in uppercase letter when the coordinate is fixed, following this protocol:

  • "---": 3D free point

  • "--z": 3D point constrained on Z

  • "  -": 1D free point

  • "  z": 1D point constrained on Z

  • "XYz": 3D point with fixed XY and constrained on Z

  • "--R": remote free 2D point

3.7. COR Covariance Matrix File

If a COR Covariance Matrix File has been given in Project Configuration, all the variances and covariances between coordinates constraints observations will be replaced by the values found in the .csv file.

The .csv file must have the same format as the one of Export Variance-Covariance Matrix tool.

This can be used to place a new set of observations in the exact same reference as an old network.

Note

Fixed points are not affected by this since they have no coordinates constraints observations.

Note

This is not used in Internal Constraints mode since all coordinates constraints observations are discarded.

Note

The covariances are not used in Monte-Carlo Simulation.