Arc Digital Raster Graphics (ADRG)
The ADRG comprises data originally produced by the National Imagery and Mapping Agency (NIMA) in the United States. These data are derived from one or more paper graphic products transformed into digital data by raster scanning at a nominal resolution of 100 microns (254 lpi) and in 24-bit RGB color.
These products are transformed according to the Equal Arc-Second Raster Chart/Map (ARC) system frame of reference. The ARC system divides each hemisphere into nine zones of ten degrees of latitude to minimize distortion.
The ADRG uses a rectangular coordinate projection based on the datum of the World Geodetic System 1984 (WGS84).
 The Arc Digital Raster Graphics (ADRG) product is no longer distributed. The following information is only maintened as a reference.
The primary sources are conventional map sheets dated from 1984 to 1991, based on the National Topographic System (NTS). The geographic data sets generated by scanning these maps are then presented as distribution rectangles. Each distribution rectangle may contain one or more data sets. The group of distribution rectangles in a series at a specific scale is the equivalent of a seamless world database of geospatial raster data in which each pixel has a distinct geographic location (georeferenced data).
The main purpose of these data is to serve as a raster display background for different applications.
ADRG had producted at two scales for Canada. Partial geographic coverage of Canada is available at the 1:50 000 scale; coverage at the 1:250 000 is nearly complete.
This information is copied from: http://www.cits.rncan.gc.ca/cit/servlet/CIT/site_id=1&page_id=1-005-002-006.html
IADRG CADRG is not available to the author of these pages. You are advised to join the Radio Mobile user group at Yahoo for more information.
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