The projection distorts both area and angles, that is, it is neither equal area nor conformal. In the Equirectangular projections used in the ARC system, meridians and parallels are straight lines of constant spacing, and meridians and parallels intersect at right angles. Parallels (lines of latitude) are circles centered at the respective pole. Meridians (lines of longitude) are straight. In the Polar Azimuthal Equidistant projections used in the ARC system, all points on the map are at the correct azimuth (direction) and proportionally correct distance from the respective pole. The ARC system is described in MIL-A-89007 (the ADRG specification) and is used by CADRG, ECRG, CIB and ECIB. Each of the (16) non-polar zones use an Equirectangular projection with the standard parallel being the midpoint latitude for the zone. The (2) polar zones use the Azimuthal Equidistant projection. Additional Point: An additional point is a route point associated with a turn point typically used to provide auxiliary information about its turn point.ĪRC Digitized Raster Graphic: a set of digitized maps (usually from scanned in paper charts) transformed into ARC system.Įqual Arc-Second Raster Chart/Map: The ARC system divides the surface of the earth ellipsoid into 9 latitudinal bands per hemisphere called zones.
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