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GfsVariableTerrain defines a variable containing the average terrain height according to a terrain database. The value of the variable is maintained as the average of the terrain database heights contained in a given cell. This is true even when the mesh is dynamically refined i.e. the height values of newly created cells are recomputed using the terrain database (rather than being interpolated from the parent cell as is the default).

For GfsRiver simulations, GfsVariableTerrain can optionally perform a (non mass-conserving) reconstruction of the depth which preserves flat water surfaces (reconstruct = 1).

The syntax in parameter files is

[ GfsVariable ] {
  path = PATH
  basename = BASE1,BASE2,BASE3
} { reconstruct = 1 }

See GfsRefineTerrain for a description of path and basename. The second parameter block is optional (and can be used only for GfsRiver simulations) and specifies whether to also reconstruct the depth (the default (reconstruct = 0) is to use mass-conserving depth reconstruction).

In addition to the variable containing the average terrain height, GfsVariableTerrain also defines additional variables which give further statistics extracted from the terrain database. If the average terrain height is called "T" for example (using the parameter passed to GfsVariable), the following additional variables will be defined:

the number of samples in the terrain database used to reconstruct the terrain in a given cell,
the minimum elevation of any sample in the terrain database belonging to a given cell,
the maximum elevation of any sample in the terrain database belonging to a given cell.
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