What map projections are used in The National Map tiled base map services and dynamic overlay services?
The projection used for all tiled base map services in The National Map is the World Geodetic System 1984 (WGS 84) Web Mercator (Auxiliary Sphere) so that base map services can be used in combination with other common viewers. See Spatial Reference SR-ORG:6928 and Spatial Reference SR-ORG:7483.
Dynamic overlay services are in WGS84 (see Spatial Reference EPSG:4326) but can be reprojected as needed. In the past, USGS map services were in WGS 84 with units of geographic decimal degrees, but the WGS 84 Web Mercator (Auxiliary Sphere) projection was implemented to allow users the greatest level of freedom in mixing these services with other commonly used web map applications that exist today.
Related
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 directions True distances...
What is the projection, horizontal datum, vertical datum, and resolution for a USGS digital elevation model (DEM)?
Projection : 3DEP DEMS have different projections/coordinate systems depending on the product: 1/3-, 1-, and 2-arc-second (also the discontinued 1/9-arc-second) DEMs are not projected. They are all in geographic coordinates (latitude/longitude). 5-meter DEMs (Alaska only) are Alaska Albers Equal Area. 1-meter DEMs are in Universal Transverse Mercator (UTM). Original Product Resolution (OPR) DEMs...
What are the projection, horizontal and vertical datum, format, and distributed tile extent of 3D Elevation Program (3DEP) contours?
Contours are not projected, but are provided in geographic coordinates (latitude and longitude) in units of decimal degrees, and horizontally referenced to the North American Datum of 1983. Contour elevation values are vertically referenced to the North American Vertical Datum of 1988. Contours are staged in Esri File Geodatabase 10.1 or Shapefile format, and distributed in 1x1 degree tiles.
What projection are the imagery services in The National Map viewer?
Imagery services in The National Map (TNM) use WGS 1984 Web Mercator (Auxiliary Sphere). The USGS ImageryOnly Service (under Base Maps) is cached (pre-generated) at this projection. Imagery services can be easily reprojected to many other popular projections for use in GIS desktop applications as background services. Learn more: Training videos for using The National Map Products and Services
Related
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 directions True distances...
What is the projection, horizontal datum, vertical datum, and resolution for a USGS digital elevation model (DEM)?
Projection : 3DEP DEMS have different projections/coordinate systems depending on the product: 1/3-, 1-, and 2-arc-second (also the discontinued 1/9-arc-second) DEMs are not projected. They are all in geographic coordinates (latitude/longitude). 5-meter DEMs (Alaska only) are Alaska Albers Equal Area. 1-meter DEMs are in Universal Transverse Mercator (UTM). Original Product Resolution (OPR) DEMs...
What are the projection, horizontal and vertical datum, format, and distributed tile extent of 3D Elevation Program (3DEP) contours?
Contours are not projected, but are provided in geographic coordinates (latitude and longitude) in units of decimal degrees, and horizontally referenced to the North American Datum of 1983. Contour elevation values are vertically referenced to the North American Vertical Datum of 1988. Contours are staged in Esri File Geodatabase 10.1 or Shapefile format, and distributed in 1x1 degree tiles.
What projection are the imagery services in The National Map viewer?
Imagery services in The National Map (TNM) use WGS 1984 Web Mercator (Auxiliary Sphere). The USGS ImageryOnly Service (under Base Maps) is cached (pre-generated) at this projection. Imagery services can be easily reprojected to many other popular projections for use in GIS desktop applications as background services. Learn more: Training videos for using The National Map Products and Services