bearing in mind different aircraft have their sensors in different locations.
That's not relevant though, because the aircraft is being sensed, rather than doing the sensing, so its sensors don't come into it.
If I recall correctly, the altitude of the aircraft would be with respect to Mean Sea Level, whereas depths in nautical charts are relative to Mean High Water Springs. You would therefore have to subtract half the tidal range (at Spring tide) from your calculation.
I was blessed with a very wise Chemistry teacher, who recognised that some of us would inevitably want to play with explosives whether we were allowed to or not, and set up an after school club to enable us to do it in a slightly more controlled environment...