Values are in meters. To convert from NAVD88 to MHHW tidal datum, subtract the conversion raster from a DEM with NAVD88 elevation values.

NAVD88_MHHW_NC

Format

RasterLayer:

dimensions

6197 X 6775 pixels

resolution

50 meter

crs/projection

UTM zone 18

value range

-0.99, 0.7606

...

Source

https://coast.noaa.gov/htdata/Inundation/TidalSurfaces/NOAA_OCM_MHHWInterpolatedSurface.zip