[Proj] New NGA documents on UTM/UPS/MGRS; time to update proj.4 implementation of UTM?

[Charles Karney]

NGA has recently published

   Universal Grids and Grid Reference Systems, Feb 2014,
   https://nsgreg.nga.mil/doc/view?i=4057

   The Universal Grids and the Transverse Mercator and Polar
   Stereographic Map Projections, Mar 2014
   https://nsgreg.nga.mil/doc/view?i=4056

These are revisions of

   TM8358.1: Datums, Ellipsoids, Grids and Grid Reference Systems,
   Sep 1990
   http://earth-info.nga.mil/GandG/publications/tm8358.1/pdf/TM8358_1.pdf

   TM8358.2: The Universal Grids: Universal Transverse Mercator (UTM) and
   Universal Polar Stereographic (UPS), Sep 1989
   http://earth-info.nga.mil/GandG/publications/tm8358.2/TM8358_2.pdf

NGA is now recommending the algorithms implemented in etmerc for the UTM
system.  So it would probably be a good idea if proj.4 had "utm" hooked
up to "etmerc" instead of the older (and less accurate) "tmerc"
algorithm.

See also
   http://trac.osgeo.org/proj/ticket/222

-- 
Charles Karney <charles.karney at sri.com>
SRI International, Princeton, NJ 08543-5300

Tel: +1 609 734 2312
Fax: +1 609 734 2662