new composite area FFE not working as expected

[panosatha]

hydomt_fiat version checks

• I have checked that this issue has not already been reported.
• I have checked that this bug exists on the latest version of hydomt_fiat.

Reproducible Example

The way the FFE of the new composite areas is not as expected. If datum is selected, the elevation is immediatelly used as FFE.

Current behaviour

The way the FFE of the new composite areas is not as expected. If datum is selected, the elevation is immediatelly used as FFE.

Desired behaviour

A comparison to the ground elevation should be made. Same goes for base flood elevation as reference.

Allow for different heights per polygon as well!

Task list

• correct code for datum
• correct code for base flood elevation
• allow different height per polygon
• check use

Additional context

No response