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Background:

ArcGIS Desktop 10.6, Spatial Analyst

I have two bare-earth DEMs, derived from lidar, acquired on different dates. I need to subtract one DEM from the other as part of a stream erosion study.

The DEMs are in different horizontal coordinate systems, so I will project one raster to match the other prior to any analysis.

Additionally, they have different geoids (03 vs. 12B), although they have the same vertical coordinate system (NAVD88).

According to the first answer to Are LiDAR datasets with same vertical datum, but based on different geoids comparable?, I need to correct for the different geoids or else I will have systematic deviations in the elevation values, adding error to any resulting analysis.

The Problem:

The ArcGIS Project Raster tool does not have the option to specify the output geoid (in my case, 03 is required). Below is a screenshot of the tools's Z-Coordinate System tab.

How/where is the output geoid specified?

enter image description here

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ArcGIS doesn't support GEOID03 yet as of ArcGIS Desktop 10.6.1 and ArcGIS Pro 2.2.

Some possible workarounds...

Convert GEOID03 into a raster format supported by ArcGIS and use raster calculations to convert the z (cell) values into ellipsoid heights. Redefine the raster's vertical coordinate system to NAD83 (which one?) ellipsoid heights. Then convert back to NAVD88 using the GEOID12b transformation.

Check VDatum from NOAA, but it supports individual point or ASCII file of points only.

  • Thanks! If not 03, then what geoid{s} does ArcGIS support? Reading between the lines of your answer I'm lead to believe that only 12b is supported. Is that correct? – Stu Smith Aug 8 '18 at 0:55
  • For the US, yes. EGM84, 96, and 2008. A few other countries. – mkennedy Aug 8 '18 at 5:09

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