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Converting NAVD88 linear units from Meter to Feet

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09-18-2017 07:24 AM
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HannesZiegler2
by
Frequent Contributor
‎09-18-2017 07:24 AM

I have a raster DEM that has the vertical coordinate system NAVD88 (height) with linear units Meter. 

I would like to convert the linear units to US_Feet. As far as I know, ArcGIS does not support conversion between vertical datum. Since the datum remains the same (NAVD88), I assume I can use raster calculator to apply the following transformation to each cell value:

Value * (39.37/12)                  {Convert linear unit from Meter to US_Feet)

However, the metadata would still state that the units are in Meter.

So, I have a few questions about converting linear units of a vertical datum. Is applying the above transformation valid? How does this affect the vertical datum stored in the metadata (i.e. if I were to now use VDATUM to convert to NAVD88 to NGVD29, how would my cell values be affected)? After using raster calculator, can I just re-define the projection (using define projection tool) to from NAVD88 (height) to NAVD88 (height) (ftUS)?

Thank you!

1 Reply
MelitaKennedy
by Esri Notable Contributor
Esri Notable Contributor
‎09-20-2017 01:19 PM

Vector data now support some vertical transformations starting with ArcGIS Desktop 10.4.1 and ArcGIS Pro 1.4 (Project tool, on-the-fly in Pro 2.1) although your use case is only indirectly supported (I know, I know!). Anyway, raster support for transformations is coming later, possibly in 10.6 / Pro 2.1.

Your workflow should work, apply the scaling then redefine the vertical coordinate system.

Melita