Geospatial Data

Scanned products are not georectified. If a customer needs them georectified they will have to do the registration themselves or have that process performed by a provider of value added services.  
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...
USGS DLG files must be translated into DXF before AutoCAD can read the files. Here is one way this can be accomplished: Download a DLG to DXF converter. There are different versions of this program depending on the version of AutoCAD. DLGTODXF -...
That depends on what kind of reprojection you want to do. In some cases, if you want to reproject from one datum to another (specifically NAD 27 to NAD 83 or NAD 83 to NAD 27), a simple xy shift will suffice. This shift will not introduce measurable...
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...
Yes, the National Atlas offers plenty of choices in page-size maps. Please see our Printable Maps page for the latest list of the printable maps we offer. In addition, the following sites have links to United States maps in formats appropriate for...
Data are offered in both compressed ARC workspaces and compressed SDTS transfer format.