I am a little confused about the new dike file. For a grid identified as dike, what is the relationship between its value in the dike location raster and that in the DEM file? Thanks.
The non null and positive value of the dike grid file is the elevation assigned to that particular cell, no matter the value from the DEM. In other words, if the cell area is covering the dike, its assigned elevation is from the dike grid file, otherwise it is from the DEM. If your dike heights data are from the ground level, then you should first add the elevation of the ground (may be from the DEM) so that dike elevations are from MTL and then create a new dike grid file.
Once the elevations are assigned, for all non dike cells the usual elevation adjustments occur to refer elevation to MTL, account for subsidence, historic SLR, etc.
In the next release the dike elevations will be referred to NAVD88.
Hope it helps,
Very helpful! Many thanks!