USGS File Types: DLG, DRG and DOQ File Types
The USGS has been driving force in GIS. some of the USGS formates date back to the 1980s just when Geographic Information System was emerging from its roots.
What you’ll find in this article are three USGS positions used to store GIS data.
These three USGS file types are:
DIGITAL LINE GRAPH (DLG) is a vector file produced on customary paper topographic maps. For instance, this incorporates township and extents, shape lines, streams, lakes, streets, railways, and towns.
DIGITAL RASTER GRAPHIC (DRG) are pictures of a U.S. Geographical Survey (USGS) standard arrangement topographic map georeferenced to the Universal Transverse Mercator projection.
DIGITAL ORTHOPHOTOS QUADRANGLE (DOQ) is a geometrically-adjusted orthophotos photo at a size of 1:40,000.
Let’s explore USGS formats in a bit more detail:
What is a Digital Line Graph (DLG)?
Digital Line Graph (DLG) is a vector information group created and disseminated by the United States Geological Survey (USGS).
DLGs depict data about geographic highlights about the landscape. Moreover, it incorporates managerial, hydrography, transportation, man-made highlights, and the sky is the limit from there. As a feature of the National Mapping Program, the USGS arranged DLGs at medium to huge scopes.
Also, all DLG information circulated by the USGS has a full structure of characteristic codes. Further to this, topology has passed a level of value control checks.
You can download Digital Line Graphs (DLG) from USGS Earth Explorer. Under the informational collections tab, click the “Advanced Line Graphs” alternative. From here, it’s a matter of picking DLG 1:100K and DLG Large Scale at that point adding it to your cart.
What is a Digital Orthophotos Quadrangle (DOQ)?
Digital Orthophotos Quadrangle (DOQ) is a geometrically-corrected photo delivered by the USGS. At around 1-meter pixel resolution, the spatial goals are at 1:40,000.
During the 1980s, GIS was beginning to create. Accordingly, the USGS began creating DOQs as a perspective. DOQs started creation in 1991 by the USGS Western Mapping Center. Be that as it may, it was a fleeting exertion, as DOQ creation moved to the private area in 2000.
You can download Digital Orthophotos Quadrangle on the USGS Earth Explorer. Under the informational indexes tab, click the “Aerial Imagery” alternative and select the DOQ option.
What is a Digital Raster Graphic?
Digital Raster Graphics (DRG) are computerized rendition maps of USGS fine to medium scale topographic maps. DRGs are standard USGS topographic maps however they have map collar information.
Each DRG has a Universal Transverse Mercator projection utilizing the North American Datum 1983. For instance, includes in these topographic maps incorporate symbolism (NAIP), streets (Interstate, course, slope, and neighborhood streets), toponymy names, hydrography (rivers, lakes), elevation contours, and boundaries.
The History of USGS Formats
TIGER has been discharging TIGER/Line documents for more than 20 years. During the 1980s, the US Census Bureau spearheaded the making of GBF/DIME inclusion documents. For every TIGER record, it utilized Dual Independent Map Encoding (DIME) for the encoding structure. Likewise, the record design produced for putting away the DIME-encoded information was the Geographic Base Files (GBF).
During this same time, the USGS was building up its own GIS information called Digital Line Graphs (DLGs). DLGs are at a size of 1:100,000 which incorporates transportation, hydrography, and United States limits. The two government organizations worked together to construct a national geospatial database consolidating their information. As a part of this initiative, they included the DLG file in GBF/DIME coverage files.