[Proj] Map projection used for CADRG polar areas?

Mikael Rittri Mikael.Rittri at carmenta.com
Wed Oct 22 04:34:52 EST 2014

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

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