The Offset Z tool in Virtual Surveyor allows you to adjust the elevation of the DSM with a constant value, in just a few steps.

Offset Z appears in the TOOLS tab when a DSM (Elevation Terrain) is selected.


Usage Guide

  1. Select the Elevation Terrain in the Project View.
  2. Go to the TOOLS tab.
  3. Set the offset value in the Offset Z box.
    1. Positive values move the terrain up.
    2. Negative values move the terrain down.
  4. Press Enter.
    1. The Elevation Terrain item is moved up or down according to the offset value setting.

You can see what your Offset Z value is in the Selection Box when the Elevation Terrain item is selected.

When to Use the Offset Z Tool

Change the Vertical Reference

You receive data from a provider who produced the data in the wrong coordinate system with an incorrect vertical reference. E.g., the data you received is set in UTM and ellipsoidal height while you need it in a projected coordinate system and your elevation at NAVD88. 

You can reproject the horizontal coordinate system and fix the vertical reference by using Offset Z to quickly adjust the ellipsoidal height to the geoidal or local height.

Correct the Average Error

After you run Check Points in Virtual Surveyor, your data has an average error that needs to be corrected. You can use the average error as a constant to fill in the offset. 

You can apply an Offset Z to the terrain that corrects the average error and improves vertical accuracy by adjusting the Elevation Terrain to independently measured check points.

Tips and Tricks

  • You can select multiple Elevation Terrains in the Project View and apply the Offset Z settings to all of them simultaneously.