Converting NAVD88 linear units from Meter to Feet

HannesZiegler2 — Mon, 18 Sep 2017 14:24:11 GMT

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!

Re: Converting NAVD88 linear units from Meter to Feet

MelitaKennedy — Wed, 20 Sep 2017 20:19:09 GMT

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

topic Converting NAVD88 linear units from Meter to Feet in Coordinate Reference Systems Questions

Converting NAVD88 linear units from Meter to Feet

Re: Converting NAVD88 linear units from Meter to Feet