The material polygons in the cross section editor should match how the materials were mapped at the land surface (e.g., a published geologic map). In geological terms, these are called "outcrops." I would like to be able to import a shapefile showing a map of these outcrops at the land surface and then display these different materials along the top arc of the cross section. This would guide the manual editing of arcs that intersect the land surface, because you need to know where these arcs should intersect the land surface. Arc Hydro Groundwater does this very well, so why is this not available in GMS? The attached file shows how this looks in Arc Hydro Groundwater.