[Proj] Still trying to get SPCS Alaska Zone 1 working!

[Anthony Dunk]

I found the answer to my own question - finally...

I found that I needed to add the +no_uoff parameter to get the same
results as Corpscon and Mapinfo.

The new command string is:

cs2cs +proj=latlong +a=6378137.0 +rf=298.257222 +to +proj=omerc
+a=6378137.0 +rf=298.257222 +lat_0=57d00'00.000N +lonc=133d40'00.000W
+alpha=-36.8698976458 +k_0=0.9999 +no_uoff +x_0=5000000 +y_0=-5000000

If I enter lon=133d40'00.000"W and lat=57N, now I get Easting=818676.73
and Northing=575097.69.

According to one of Gerald Evenden's documents "In some cases, an
offset in the pre-rotated axis may need to be suppressed with the
+no_uoff option.". Its gobbledegook to me - but hey it works!

Anthony.


--- Anthony Dunk <AnthonyD at rocketmail.com> wrote:

> Hi,
> 
> Can anyone explain to me why the US Govt document on NAD83 State
> Plane
> Coordinate System (see link below) says that the origin for Alaska
> Zone
> 1 is lat=57N lon=133'40W or Easting=5,000,000, Northing=-5,000,000,
> but
> when I run the Corpscon program with the appropriate setup it
> projects
> this lat/lon to Easting=818676.713, Northing=575097.689 ? I also
> found
> that MapInfo projects it to exactly the same Easting/Northing as
> Corpscon.
> 
> If I use PROJ's cs2cs command (Rel 4.4.7 31 March 2003) to convert
> these lat/lon coordinates using the following command:
> 
> cs2cs +proj=latlong +a=6378137.0 +rf=298.257222 +to +proj=omerc
> +lonc=-133.6666666667 +lat_0=57 +alpha=-36.8698976458 +k=0.9999
> +x_0=5000000 +y_0=-5000000  +a=6378137 +rf=298.257222101
> 
> Then I get Easting=4999999.80 Northing=-5000000.0.
> 
> So, the PROJ command gives results which agree with the NAD83 SPCS
> document, but both Corpscon and MapInfo give a consistent but
> different
> result. What is going on, and who is correct ??!
> 
> Thanks,
> Anthony.
> 
> NAD83 SPCS document:
> http://www.ngs.noaa.gov/PUBS_LIB/ManualNOSNGS5.pdf
> 
> 
> 
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