Bathymetry Encoding - how to deal with overlapping canals?

[KathiSchleidt]

We recently ran into an interesting question while generating a gridded representation of bathymetry data for provision via INSPIRE WCS: what elevation do we use for grid cells where we have two elevation values, as two canals cross at this point.

To my view, the decision depends on if the elevation data being provided is DTM or DSM. I would provide as follows:

• DTM: provide the lower level, bottom of the lower canal, as this is the bottom of the natural world
• DSM: provide the upper level, bottom of the upper canal, as this is a "built surface"

Any ideas or opinions on this?

(I'm posting this in the general section as it also applies to the TIFs being provided by many MS)