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Mapping, Remote Sensing, and Geospatial Data

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

Filter Total Items: 200

What is a digital orthophoto quadrangle (DOQ) or orthoimage?

A digital orthophoto quadrangle (DOQ)--or any orthoimage--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, an orthoimage has a uniform scale, so it can be used as a base map...

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What is a digital orthophoto quadrangle (DOQ) or orthoimage?

A digital orthophoto quadrangle (DOQ)--or any orthoimage--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, an orthoimage has a uniform scale, so it can be used as a base map...

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What does the term UTM mean? Is UTM better or more accurate than latitude/longitude?

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 own implementation of the UTM system, called the...

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What does the term UTM mean? Is UTM better or more accurate than latitude/longitude?

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 own implementation of the UTM system, called the...

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What is the National Hydrography Dataset (NHD)?

The National Hydrography Dataset (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 system.These data are...

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What is the National Hydrography Dataset (NHD)?

The National Hydrography Dataset (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 system.These data are...

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What is a digital elevation model (DEM)?

A Digital Elevation Model (DEM) is a representation of the bare ground (bare earth) topographic surface of the Earth excluding trees, buildings, and any other surface objects. DEMs are created from a variety of sources. USGS DEMs used to be derived primarily from topographic maps. Those are being systematically replaced with DEMs derived from high-resolution lidar and IfSAR (Alaska only) data...

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What is a digital elevation model (DEM)?

A Digital Elevation Model (DEM) is a representation of the bare ground (bare earth) topographic surface of the Earth excluding trees, buildings, and any other surface objects. DEMs are created from a variety of sources. USGS DEMs used to be derived primarily from topographic maps. Those are being systematically replaced with DEMs derived from high-resolution lidar and IfSAR (Alaska only) data...

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In what scale are the data in the National Hydrography Dataset (NHD)?

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 at higher resolutions. In 2010, a decision was made...

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In what scale are the data in the National Hydrography Dataset (NHD)?

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 at higher resolutions. In 2010, a decision was made...

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How large is the North American Datum (NAD) 27 to NAD 83 shift?

Within the conterminous 48 states, the North American Datum of 1927 (NAD 27) to the North American Datum of 1983 (NAD 83) shift of the latitude/longitude graticule (lines showing parallels of latitude and meridians of longitude for the earth) is in the range of 10-100 ground meters. Changes to UTM values are generally larger, around 200 meters, and changes for other coordinate systems are...

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How large is the North American Datum (NAD) 27 to NAD 83 shift?

Within the conterminous 48 states, the North American Datum of 1927 (NAD 27) to the North American Datum of 1983 (NAD 83) shift of the latitude/longitude graticule (lines showing parallels of latitude and meridians of longitude for the earth) is in the range of 10-100 ground meters. Changes to UTM values are generally larger, around 200 meters, and changes for other coordinate systems are...

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How much distance does a degree, minute, and second cover on your maps?

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 and the meridians converge.At 38 degrees North latitude (which passes through Stockton California and Charlottesville Virginia):One degree of latitude equals approximately 364,000 feet (69...

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How much distance does a degree, minute, and second cover on your maps?

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 and the meridians converge.At 38 degrees North latitude (which passes through Stockton California and Charlottesville Virginia):One degree of latitude equals approximately 364,000 feet (69...

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What is the State Plane Coordinate System? Can GPS provide coordinates in these values?

The State Plane Coordinate System (SPCS), which is only used in the United States, is a plane coordinate system (north-south and east-west lines are perpendicular) in which each individual state has between one to six zones, depending on the state's size and shape. This coordinate system’s high level of accuracy is achieved through the use of relatively small zones. The State Plane Coordinate...

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What is the State Plane Coordinate System? Can GPS provide coordinates in these values?

The State Plane Coordinate System (SPCS), which is only used in the United States, is a plane coordinate system (north-south and east-west lines are perpendicular) in which each individual state has between one to six zones, depending on the state's size and shape. This coordinate system’s high level of accuracy is achieved through the use of relatively small zones. The State Plane Coordinate...

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How can I find survey benchmark and triangulation station information?

Most survey marks were set by the U.S. Coast & Geodetic Survey (now called the National Geodetic Survey); information for those marks is available online. For further assistance, contact the National Geodetic Survey at 301-713-3242 or ngs.infocenter@noaa.gov. For information about marks set by the USGS, contact the National Geospatial Technical Operations Center at tnm_help@usgs.gov. Learn more...

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How can I find survey benchmark and triangulation station information?

Most survey marks were set by the U.S. Coast & Geodetic Survey (now called the National Geodetic Survey); information for those marks is available online. For further assistance, contact the National Geodetic Survey at 301-713-3242 or ngs.infocenter@noaa.gov. For information about marks set by the USGS, contact the National Geospatial Technical Operations Center at tnm_help@usgs.gov. Learn more...

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How are different map projections used?

The method used to portray a part of the spherical Earth on a flat surface, whether a paper map or a computer screen, is called a map projection. No flat map can rival a globe in truly representing the surface of the entire Earth, so every flat map misrepresents the surface of the Earth in some way. A flat map can show one or more--but never all--of the following: True directionsTrue distancesTrue...

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How are different map projections used?

The method used to portray a part of the spherical Earth on a flat surface, whether a paper map or a computer screen, is called a map projection. No flat map can rival a globe in truly representing the surface of the entire Earth, so every flat map misrepresents the surface of the Earth in some way. A flat map can show one or more--but never all--of the following: True directionsTrue distancesTrue...

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How are UTM coordinates measured on USGS topographic maps?

The UTM (Universal Transverse Mercator) coordinate system divides the world into sixty north-south zones, each 6 degrees of longitude wide. UTM zones are numbered consecutively beginning with Zone 1, which includes the westernmost point of Alaska, and progress eastward to Zone 19, which includes Maine. If UTM ticks are shown on a USGS topographic map, the zone is indicated in the credit legend in...

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How are UTM coordinates measured on USGS topographic maps?

The UTM (Universal Transverse Mercator) coordinate system divides the world into sixty north-south zones, each 6 degrees of longitude wide. UTM zones are numbered consecutively beginning with Zone 1, which includes the westernmost point of Alaska, and progress eastward to Zone 19, which includes Maine. If UTM ticks are shown on a USGS topographic map, the zone is indicated in the credit legend in...

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Are all US Forest Service maps available from the USGS?

Paper copies of all U.S. Forest Service maps--including Forest Visitor Maps, National Forest Atlases, and Wilderness Maps--are sold through the online USGS Store, though they might not always be in stock. Paper maps are also available for purchase at some Forest Service offices and at some retail outlets.Order paper maps for individual national forests using the online USGS Store. Enter the name...

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Are all US Forest Service maps available from the USGS?

Paper copies of all U.S. Forest Service maps--including Forest Visitor Maps, National Forest Atlases, and Wilderness Maps--are sold through the online USGS Store, though they might not always be in stock. Paper maps are also available for purchase at some Forest Service offices and at some retail outlets.Order paper maps for individual national forests using the online USGS Store. Enter the name...

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