Getting the WGS84 Ellipsoidal Height

We’ve been struggling to get our elevations from the Lidar to match up with our known ground control elevations. When processing, we know that we’re supposed to enter the ellipsoidal height of our base station to the phase centre of the receiver. Normally our controllers are loaded with Geoid models as we do a lot of terrestrial surveying and only recently started with Lidar and Rock.

Our control points have been set with rovers that have geoid models embedded so I’m thinking that our issue has been that when we grab the exact location of our base and determine height to phase centre, we are referencing the Orthometric Height rather than the Ellipsoidal Height as we are told to do. Most people have the opposite problem and need to load a geoid model to get decent ground elevations. My theory is that we should be setting our base station point using no geoid model applied and that way it should provide us with ellipsoidal height instead of orthometric. Orthometric heights are from ground to the geoid and we want to avoid this all together for our data processing. We seem to be getting a 2-3 foot bust in the vertical.

Has anyone had this issue? We are using Trimble TSC3 and R8 Receiver.

You can just adjust the z in the cloud. Mine is always off like 100 feet but I just fix it by adjusting the point cloud in the rock cloud. It is easy.

You mention adjusting the z in the cloud, how is this done. In Harrison’s explainer videos, he says that if we don’t know the precise position of the base, we can just use whatever auto-populates, and that we can adjust this in the cloud. But I don’t see where we can do this. Video reference:

In the cloud look in the top right and see the second took- it has boxes for x/y/z - you simply move them however much you need. I usually just add a point on the ground near my base then do the math and adjust accordingly- then I refine it using the up and down arrows for each.

Hint: Hold shift +arrows to move it faster.

Does this change the LiDAR data? It seems fairly arbitrary to be moving the dataset up and down based on looks.

It changes its position once you click save.