Applicable plans
Valley Ridge Peak

Virtual surveyor can help you to align you photogrammetry outputs with your elevation datum

The proper elevation datum needs to be set in your photogrammetry process. That is the processing step before you start working in Virtual Surveyor. Nevertheless, most of the time your image processing software only exports Ellipsoidal height unless you use GCPs or adjust the 3D model to a global or local geoid model.

Virtual Surveyor provides a quick and easy way to adjust your data to local heights. Keep in mind this process is not suited to larger areas!


  1. Draw a boundary around the area of interest.
  2. Clip the terrain within that boundary item. 
  3. Select the boundary and go to the SELECTION TOOLS tab.
  4. Set the offset value in the Terrain group.
  5. Click on Offset Within.

Import data

Drag and drop your drone survey dataset (Orthophoto + DSM)  into the project view to create a Terrain State

Area of interest clipping

Draw a boundary around your entire site to define your area of interest. Select that boundary and your drone survey (DSM and Ortho) and go to the SELECTION TOOLS tab. Click on Clip button.

Terrain Offset

Select the boundary and go to the SELECTION TOOLS tab. In the terrain group, set the offset value in the Level box and click on Offset Within button.

Tips and Tricks

  • Objects (points, polylines, surfaces...) placed on the initial terrain will not follow the offset. The best practice is to first offset the terrain and then perform your survey.
  • You can remove the offset via the project view offset item. The terrain will revert to its original state.
  • Note that with the 'Offset Within', the variability of your terrain within the boundary is preserved. This is not the case when you use the 'Modify Terrain' operation.
  • Refer to the site supervisor to determine the offset value between ellipsoidal height and local height. You can also use the geoid height value if you want to offset from ellipsoidal height to geoidal height. Refer to you national geographic institute to know more about the geoid height values.