[Proj] Alaska State Plane Coordinates (NAD83) - Hotine Oblique Mercator ??

[Oscar van Vlijmen]

> From: Anthony Dunk <AnthonyD-rocketmail.com>

> Has anyone successfully implemented support for the Hotine Oblique
> Mercator for the Alaska SPCS Zone 1 (5001) using PROJ4 ?

....

> Are these parameters correct ??

Don't think so.

One 'official' test point from the GCTP test suite, including the header
information:

Alaska, Zone 1 AK_1 6101 5001
STATE PLANE PROJECTION PARAMETERS:
   Zone:      5001
   Datum:     NAD 27

etc.


I forgot: there are no easy to find test points for Alaska 5001 under NAD83.

Therefore my test with the earlier mentioned NAD27 GCTP point, but now with
the correct parameters for NAD83:
(Data from the manual page 63,
http://www.ngs.noaa.gov/PUBS_LIB/ManualNOSNGS5.pdf)

// first set GRS80
lat = 58.5; lon = -135;
lat0 = 57; lonc = -133d40m;
alfac = -36.869898; gamma = "";
k0 = 0.999900; x0 = 5e6; y0 = -5e6;
Result: x = 4922256.91413097; y = -4832195.16685546

By the way, asin(-0.6) = atan(-3/4), mentioned in the 'manual'.

I hope others can verify the results.