Zipfile Readme

Each Zipfile contains Military Grid Reference System (MGRS) Data.

The 100m MGRS data layers have been derived by the GeoPlan Center from the National Geospatial-Intelligence Agency (NGA) 100KM MGRS data layers for each UTM Zone’s MGRS Grid Zone Designator (GZD).

Each MGRS GZD File Geodatabase (ArcGIS 9.3) has been placed in it’s own folder.  Each folder contains the metadata for each data type (100km, 10km, 1km, 100m) found in the File Geodatabase (See MGRS FGDB Structure Below).

Example: mgrs_17s_100m

MGRS_17S_100m_esri93.gdb

– MGRS_100kmSQ_ID_17S [This is a MGRS 100km Square Identifier polygon layer]

– MGRS_17S_10km [This is a MGRS 10km Square Identifier polygon layer]

– MGRS_17S_1km [This is a MGRS 1km Square Identifier polygon layer]

– MGRS_17SKA_100m [This is a MGRS 100m Square Identifier polygon layer]

To view the NGA Worldwide MGRS GZD layer (mgrs_gzd_worldwide_wgs84) please see the mgrs_supplemental_data directory (MGRS_Supplemental_Data.gdb)

Additional Data can be downloaded that contains the following:

MGRS_Supplemental_Data.gdb (click link to get zipfile)

Please Note: These layers are only to be used for large scale cartography.

bcr

• bcr_najv_wgs84 [NORTH AMERICAN BIRD HABITAT JOINT VENTURES – 2009]
• bcrfinalg_wgs84 [NORTH AMERICAN BIRD CONSERVATION REGIONS (BCRS) – 2001]

mgrs_worldwide

• mgrs_gzd_worldwide_wgs84 [World-wide MGRS Grid Zone Designators (GZD)]

Natural_Earth

• admin_1_states_provinces_10m [Admin 1 – States, Provinces]
• lakes_10m [Natural and artificial lakes]
• populated_places_10m [Area and point labels of major physical features]
• roads_north_america_10m [Roads]
• us_parks_area_10m [Parks and Protected Lands. Includes 394 U.S. National Park Service units]
• wgs84_bounding_box_10m [Grids at WGS84 bounding box]

Please Note: MGRS_Supplemental_Data.gdb metadata can be found attached to each data layer with in the FGDB.

All Natural Earth Data Layers have been downloaded from the following website

http://www.naturalearthdata.com

Converting from MGRS to USNG

When converting from MGRS to USNG use the following projection transformation:

NAD_1983_To_WGS_1984_5
Transformation parameters calculated by the U. S. National Geodetic Survey (NGS) using CORS stations, and ties WGS 1984 to ITRF96. This transformation method should be used for the 48 contiguous states and for the state of Alaska, as well, effective with version 9.3 of ArcGIS Desktop.

MGRS Zipper Effect

The Universal Transverse Mercator (UTM) projection is a planer projection used to project the curved surface of the earth on a two-dimensional plane. In the U.S, excluding Alaska, there are approximately 12 UTM zones. Irregular grid cells with areas less than 1-kilometer square occur along the edges of each zone junction. These Zipper Cells occur because mapping the three-dimensional spherical earth on a two-dimensional plane creates distortions which may appear as sliver polygons.

SOURCE:

http://www.fws.gov/southwest/AboutUs/LCC/docs/GP_LCC_ReportFinalDraft_Hanni.pdf

Additionally there is also a small North and South MGRS zipper effect where seams with slivers are also a by-product of the transformation of the earth from a round object to a flat one, however, this by-product is more easily observed in the East and West MGRS seams.