Geospatial Data

UTM coordinates are measured on the map by subdividing the 1000 meter grid squares into tenths or hundredths. This will narrow down the coordinate to a 100 or 10 meter square. Usually the measurements are made using a simple mylar or paper scale or a...
If coordinates are to be passed on to another person it is technically necessary to report the horizontal datum and the latitude/longitude of the point (e.g. NAD 27 CONUS, 44 degrees, 7 minutes, 30 seconds north/ 104 degrees, 15 minutes, 10 seconds west...
The State Plane Coordinate System (SPCS) is a plane coordinate system (N-S and E-W lines are perpendicular) in which each individual state has from one to six zones, depending on the state's size and shape. The grid system in some states is based on the...
Generally, for the conterminous United States, the North American Datum (NAD) shift amounts to about 210 meters. This shift occurs because of the change in shape of the spheroid used to define the datum. The GRS 80 spheroid (used for NAD 83) is shorter...
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...
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...
A GIS is a computer system capable of capturing, storing, analyzing, and displaying geographically referenced information; that is, data identified according to location. Practitioners also define a GIS as including the procedures, operating personnel,...
The National Geologic Map Database Data Portal is intended to: 1) give the user a quick browse and query of our Nation's geologic maps, in a standardized format, and 2) link the user to the source information found via the NGMDB Map Catalog and Geologic...
An exhaustive database that provides bibliographic access to thousands of geologic, geophysical, and other kinds of maps available in USGS publications, Web sites, and in popular science journals.
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...