MAP COORDINATES AND DATUMS

Most students are familiar with the system of latitude and longitude map coordinates. However, most surveying and reporting of locations in the hydrologic sciences will be presented in another format:

Northings and Eastings (or the Universal Transverse Mercator Grid)

Township and Range (or the Public Land Survey System)

California Water Well Numbering - based on Township and Range

Map coordinates and elevations must be referenced to a horizontal and vertical datum. The officially adopted legal horizontal datum of the United States is the North American Datum of 1983 (NAD83). Older map coordinates may be referenced to the North American Datum of 1927 (NAD27). Conversion software is available from the National Geodetic Survey. The vertical control datum must be specified and can be NGVD29 (sea level datum of 1929) or NAVD88. The NGS has conversion software between these 2 systems.

National Geodetic Survey

http://www.ngs.noaa.gov

Map Basics from our own library

http://infodome.sdsu.edu/research/guides/maps/basics.shtml

General Maps

http://www.cnr.berkeley.edu/departments/espm/extension/MAPS.HTM