Geodesic Elevation Profiles for Planetary Bodies

[mahunter_USGS]

When creating elevation profiles with Exploratory 3D Analysis geodesic ground distances are tied to Earth, regardless of the datum for the source DEM. This was identified when creating profiles over large features on the Moon, where the difference between planar and geodesic distances is significant. After reprojecting the DEM to Moon 2000 GCS all measurements were more than 3x the real ground distance which is consistent with the radius difference.

This screenshot illustrates the error; the actual planar and geodesic measurements are in the attribute table.

[JonathanLebowitz]

Hello. You mentioned that you re-projected your DEM to GCS Moon 2000? What coordinate system was it projected from? Which transformation did you apply? I'm not aware of any out-of-the-box transformations available in ArcGIS between Earth-based and Moon-based coordinate systems.

[mahunter_USGS]

Hi, the DEM was originally in an equidistant cylindrical projection, with the same lunar datum (Moon 2000, 1737.4Km radius). Because the elevation profile documentation states that it uses the native of the DEM I was expecting that projecting to GCS would support geodesic measurements.

[JonathanLebowitz]

Hello. The Interactive elevation profile tool supports displaying geodesic distance along the profile, but the coordinate system of the scene would need to be a geographic coordinate system. There is not a way to switch between planar and geodesic distance in the tool itself, like there is with the Measure tool. That said, I do see that the Moon 2000 sphere it is not being honored in Scene Viewer with the Elevation Profile tool in ArcGIS Pro 3.6.2 whereas the Measure tool does honor it. I will investigate this as a bug. I do not believe this is an issue with your DEM, but just in case is it publicly available?

[mahunter_USGS]

Thanks! Here is the source DEM. https://astrogeology.usgs.gov/search/map/moon_lro_lola_selene_kaguya_tc_dem_merge_60n60s_59m 

[JonathanLebowitz]

We have logged a bug for this issue. Do you have the ability to open a Technical Support case to get attached to it for tracking purposes?

[mahunter_USGS]

I do not have permissions in our org to create a support ticket, but will work through our channels to initiate one, and track. I really appreciate your responsiveness.

[JonathanLebowitz]

No problem. For your records, the bug information is documented at https://support.esri.com/en-us/bug/BUG-000184143. As a side note, if the scene's coordinate system is set to a projected coordinate system based on GCS Moon 2000/WKID 104903 (e.g., PCS Moon 2000 Equidistant Cylindrical/WKID 103881), the planar distance in the interactive Elevation Profile tool appears to match the actual planar distance in the scene. I believe that you observed this as well.