A geospatial modeling system may include a geospatial model data storage device and a processor cooperating therewith for determining a void within a geospatial model data set defining a void boundary region, and selecting at least one raw fill region from within the geospatial model data set for filling the void. The processor may also cooperate with the geospatial model data storage device for adjusting elevation values of the at least one raw fill region based upon elevation differences between corresponding portions of the void boundary region and the at least one raw fill region, and updating the geospatial model based upon the adjusted elevation values of the at least one raw fill region.