For some time GMS has included the capability to use TINs with the Map->MODFLOW command. The next version of GMS will also include the capability to use Rasters with the Map->MODFLOW command similar to how TINs can be used now. In the conceptual model, the user will associate the desired Raster with the Head/Elevation assigned to a point, node, arc, or polygon. When the Map->MODFLOW command is executed the Head/Elevation for the boundary condition is extracted from the Raster using the cell center where the boundary condition is applied. The figure below shows how/where the Raster can be assigned to a point/node/arc/polygon.