A Digital Elevation Model (DEM) is a digital representation of the contours of the Earth's surface. The information is derived from elevation measurements at regularly spaced intervals. This data is published by the USGS and covers a 7.5-minute area with 30-meter resolution.
These 1:24000 scale Digital Line Graphs are currently being used as a statewide frame work for cadastral mapping.
A digital raster graphic (DRG) is a scanned image of a U.S. Geological Survey (USGS) topographic map. The scanned image includes all map collar information. The image inside the map neatline is georeferenced to the surface of the Earth. The DRG can be used to collect, review, and revise other digital data, especially digital line graphs (DLG). When the DRG is combined with other digital products, such as digital orthophoto quadrangles (DOQ) or digital elevation models (DEM), the resulting image provides additional visual information for the extraction and revision of base cartographic information.
LiDAR is a technology that measures distance through reflected light. The term LiDAR is a combination of "light" and "radar." LiDAR is used for high-resolution maps in a variety of specialized fields.