[Proj] Map projection used for CADRG polar areas?
Mikael Rittri
Mikael.Rittri at carmenta.com
Wed Oct 22 04:34:52 EST 2014
Hello,
I am reading the specification for CADRG,
http://earth-info.nga.mil/publications/specs/printed/89038/89038_CADRG.pdf .
But I am confused about the polar areas.
Section 3.5.5 says: "CADRG shall use a polar stereographic projection".
And Section 3.5.6 says "Polar frames are defined in polar stereographic
projection and non-polar frames are in the ARC projection."
But Section 3.6.2 says: "Pixel coordinates in the polar zones are
proportional to rectangular coordinates of the Azimuthal
Equidistant projection, polar aspect, spherical form (as
defined in Map Projections-A Working Manual, page 191)."
And section 30.1 says: "Polar zone equations are based on
the Azimuthal Equidistant projection, polar aspect,
spherical form."
Since Polar Stereographic is not the same thing as Azimuthal Equidistant
in polar aspect, I assume that one of the two alternatives is just a typo
(unless I am missing something). But which one is the typo of
"Stereographic" and "Azimuthal Equidistant"? Does anyone know?
Best regards,
Mikael Rittri
Carmenta
Sweden
http://www.carmenta.com
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