Frequently Asked Questions

Mapping, Remote Sensing, and Geospatial Data

The USGS provides the mapping and digital geospatial foundation for the Nation.

Filter Total Items: 199
historic topographic map of portland, or
For maps in the Historical Topographic Map Collection (1884-2006): Through time, policies have changed regarding whether or not a full UTM grid would appear on the 7.5-minute map series. Beginning in the mid 1950's, the grid was indicated by blue ticks around the map at 1000 meter spacing. In 1979, the ticks were replaced with a full-line black...
northwest US and southwest Canada elevation
The old coordinates were not wrong, just different. They are based on different earth shapes or ellipsoids and were based on the best technology at the time. Mathematically, NAD83 is a stronger datum because all previously existing horizontal stations and newer GPS surveyed stations were adjusted simultaneously. The positions within NAD27 were...
Watershed Boundary Dataset Map - Mississippi
The NHD is a combination of USGS hydrologic digital line graph (DLG) files and EPA reach files, version 3.0 (RF3). Also used were: U.S. Forest Service Cartographic Feature Files (CFF) and USGS Tagged Vector Hydro (TVH) captured from 7.5-minute printed maps. Some states also contributed their own stream layer data to the compilation of the 1:24,000...
NHDPlus, WBD,  and Catchments
Original hydrographic data were compiled to meet National Map Accuracy standards. These standards have been maintained in the process of creating the NHD. At 1:100,000 scale, ninety percent of well-defined features are within 167 feet (0.02 inches at map scale) of their true geographic position. When higher resolution data are created and...
Geologic map of the confluence of the Green and Yampa rivers, Dinosaur National Monument, Colorado/Utah
The National Geologic Map Database (NGMDB) is an archive of geoscience maps (including geology maps), reports, and stratigraphic information for the United States. The NGMDB contains information on more than 90,000 maps and related geoscience reports published from the early 1800s to the present day, by more than 630 agencies, universities,...
GIS data layers visualization
A Geographic Information System (GIS) is a computer system that analyzes and displays geographically referenced information. It uses data that is attached to a unique location. Most of the information we have about our world contains a location reference: Where are USGS streamgages located? Where was a rock sample collected? Exactly where are all...
Portion of 2012, High Resolution Orthoimage data near  Lake Union, Seattle, Wash
A digital orthophoto quadrangle (DOQ) is a computer-generated image of an aerial photograph in which displacements (distortions) caused by terrain relief and camera tilts have been removed. It combines the image characteristics of a photograph with the geometric qualities of a map. Unlike an aerial photograph, a DOQ (or any orthoimage) has a...
UTM Grid conterminous 48 United States
UTM is the acronym for Universal Transverse Mercator, a plane coordinate grid system named for the map projection on which it is based (Transverse Mercator). The UTM system consists of 60 zones, each 6-degrees of longitude in width. The zones are numbered 1-60, beginning at 180-degrees longitude and increasing to the east. The military uses their...
NHDPlus HR Hydrologic Regions Map
The NHD is a digital vector dataset used by Geographic Information Systems (GIS) to define the spatial locations of surface waters and is designed to provide comprehensive coverage of surface water data for the U.S. The NHD contains features such as lakes, ponds, streams, rivers, canals, dams, and stream gages, in a relational database model...
Digital elevation model created by an Unmanned Aerial System
USGS Digital elevation models (DEMs) are arrays of regularly spaced elevation values referenced horizontally either to a Universal Transverse Mercator (UTM) projection or to a geographic coordinate system. The grid cells are spaced at regular intervals along south to north profiles that are ordered from west to east. The USGS acquires bare-earth...
The National Map Hydrography Viewer
For the conterminous United States, Hawaii, and the Virgin Islands, medium and high resolution NHD data are available at 1:100,000 and 1:24,000-scale, respectively. NHD data are available for Puerto Rico at 1:20,000-scale, and at 1:63,360-scale in Alaska. Users are encouraged to work with their state's principal steward to produce and submit data...
Image: USGS Topographer at Work
The distances vary. A degree, minute or second of latitude remains fairly constant from the equator to the poles; however a degree, minute, or second of longitude can vary greatly as one approaches the poles (because of the convergence of the meridians). At 38 degrees North latitude, one degree of latitude equals approximately 364,000 ft (69 miles...