Adjust to geoid

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Adjust to geoid

Adjust to geoid

Adjust to geoid command applies an elevation correction to trajectory files. The command is used, for example, to transform the WGS84-based ellipsoidal elevation values of a raw trajectory file to a local height model. The input model for geoid adjustment must be provided in one of the following formats:

Points from file - text file containing space-delimited X Y dZ points.

TerraModeler surface - triangulated surface created from X Y dZ points. The model must be loaded in TerraModeler. This has the advantage that you can visualize the adjustment model.

Selected linear chain - linear element which has vertices derived from X Y dZ points.

XY are the easting and northing coordinates of the geoid model points, dZ is the elevation difference between ellipsoidal and local heights at the location of each geoid model point. Intermediate adjustment values of the model are derived by aerial (text file or surface model as input) or linear (linear element as input) interpolation between the known geoid model points.

The first two input models utilize aerial interpolation while the last input model uses linear interpolation along the linear element’s segments in order to derive adjustment values.

To adjust trajectories to a geoid model:

1. (Optional) Load a geoid model into TerraModeler.

2. (Optional) Select trajectory file(s) to adjust.

3. Select Adjust to geoid command from the Tools pulldown menu.

This opens the Adjust trajectories to geoid dialog:

adjust_trajectories_to_geoid

4. Define settings and click OK.

If Points from file is selected as the Dz model, the Geoid dz file dialog opens, a standard dialog for opening files.

5. Define the text file that contains the geoid coordinates and elevation differences and click Open.

This applies the elevation adjustment to all or selected trajectories. The modification is saved to the trajectory binary files in the active trajectory directory. An information dialog shows the minimum and maximum values of the adjustment.

SETTING

EFFECT

Process

Trajectories to adjust:

All trajectories - all trajectories in the list.

Selected only - selected trajectories only.

Dz model

Source file that provides the geoid correction model:

Points from file - text file.

Selected linear chain - linear element selected in the design file.

<name> - name of the geoid model surface loaded in TerraModeler.

Extend

Distance of a linear extension. This is only active if Dz model is set to Selected linear chain.