The US National Grid (USNG) is a ground-based gridded coordinate system based on the Universal Transverse Mercator (UTM) System and derived from the Military Grid Reference System (MGRS). As such, the basic unit of measure is the meter and positions are reported as distance north from the equator (Northings) and distance from the zone central meridian (Eastings). It provides a nationally consistent language of location in a user friendly format. The purpose of USNG is to provide a seamless, standardized system of reference for nationwide use. The primary difference between the MGRS and USNG is their datums, which describe the 3 dimensional shape of the Earth. The MGRS uses the WGS84 datum and the USNG uses the NAD83 datum. When the USNG is used with the World Geodetic System of 1984 (WGS84) datum, it is exactly the same as MGRS. Otherwise, the maximum offset between the datum is less than 2 meters (Natural Resources Canada http://www.geod.nrcan.gc.ca/faq_e.php#23), which is negligible for most applications. Relationships among the UTM coordinate system, MGRS and USNG are described here: http://www.andrewlesley.freeserve.co.uk/gps/UTMMGRS.html
The U.S. National Grid (USNG) (Federal Geographic Data Committee 2001), has the qualities needed for a grid standard that could be applicable to bird monitoring sampling. These qualities include:
The USNG is only available for the conterminous United States.
Examples of use
The US National Grid is the standard set forth by the FGDC (http://www.fgdc.gov/usng) to "create a more favorable environment fo developing location-based services within the United States and to increase the interoperability of location services applicanced with printed map products by establishing a nationally consistent grid reference system as the preferred grid for the National Spatial Data Infrastructure".
For more information
The USNG is currently available for online download as 1 km cell products, with cells labeled by 1 km and 100 km name from The USNG National Implementation Center (TUNIC) at Delta State University. These products are organized by state and UTM zone: http://mississippi.deltastate.edu/
Sampling Grids >