An ArcSDE Topographic Dataset is created from the original USGS DRG topographic maps. The quad is first projected to your the same Projection, then cropped to the map extents. The voided areas of the map are then filled with the necessary adjacent map information to make the map and Tiff file rectangular. ArcSDE Topographic Dataset images are geometrically registered at the pixel level from map to map; even from degree to degree. ArcSDE Topographic Dataset's are a contigous image eliminating overlap and transparency problems associated with other map products.