National Park Service

Inventory & Monitoring (I&M)

Base Cartography Examples

Digital Line Graphics (DLG)

Digital line graph data are digital representations of cartographic information. DLGs of map features are digital vectors converted from maps and related sources. Here are four examples of DLGs.

boundary file example


Boundaries include all state, county, city, and other national and state lands such as forests and parks.

hydrography file example


Hydrographic features include flowing water, standing water, and wetlands.

hypsography file example


Hypsographic features include elevation contours and supplementary spot elevations.

transportation example


Transportation features include roads and trails, railroads, pipelines and transmission lines.

Digital Raster Graphics (DRG)

drg example

A digital raster graphic is a scanned image of a U.S. Geological Survey standard series topographic map, including all map collar information.

Digital Orthophoto Quadrangles (DOQ)

doq example

A digital orthophoto quadrangle is a computer-generated image of an aerial photograph in which image displacement caused by terrain relief and camera tilts has been removed. It combines the image characteristics of a photograph with the geometric qualities of a map.

Digital Elevation Models (DEM)

dem example

A DEM is a digital file consisting of terrain elevations for ground positions at regularly spaced horizontal intervals.

DEMs are available in 30-meter resolution for the United States. Some areas have been reproduced at 10-meter resolution as well, though complete coverage at 10-meter resolution has not yet been achieved.

National Elevation Dataset (NED)

The NED is designed to provide national elevation data in a seamless form with a consistent datum, elevation unit, and projection. Data corrections were made in the NED assembly process to minimize artifacts, permit edge matching, and fill sliver areas of missing data.

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Last Updated: December 30, 2016 Contact Webmaster