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I have a specific problem re: projected coordinate systems. I am working with point data from IceSat2 and a LiDAR-derived DEM of Daviess county in Indiana. I am trying to compare height values for points (in shapefile format).

The DEM coordinate system comes from the data portal with reference system:

EPSG Code 2966, NAD_1983_StatePlane_Indiana_West_FIPS_1302_Feet
Units of Measure:  us_survey_feet 
Horizontal Datum:  NAD83 
Spheroid:  GRS 1980 
Vertial: GEOID NAVD1988 (elevation units of us_survey_feet)

The point data was originally taken from ICESAT2 data files which are said to have a WGS84 reference

This data set (ATL03) contains height above the WGS 84 ellipsoid (ITRF2014 reference frame)

When I write out the point shapefile, I use EPSG:4326. I then re-projected the DEM from EPSG:2966 to EPSG:4326.

When I finally sample the raster with the point shapefile, the heights are similar but offset by some ~34 meters...

Elevation Difference

I understand it's likely something simple with a disconnect between the spatial reference system and the projected coordinate system or something, but am at a loss. Please let me know a way forward!

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Your data reference two different vertical datums. You are comparing apples to oranges so the elevations will not align. See this link for a basic tutorial on different vertical datums. You can use vDatum to convert datasets between vertical datums.

ArcGIS Pro now allows for vertical datum conversions but I have not tried this yet. You will most likely need to download and install the ArcGIS Coordinate System executable available from ESRI.

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  • Hey man thank you so much for this, I knew it was something simple but didn't know which tool might get me out of jam. Let me give this a try and then ill mark it as resolved. Cheers
    – jameshgrn
    Jul 22 at 17:00

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