[Proj] NAD conversion test points?

William Kyngesburye woklist at kyngchaos.com
Tue Mar 9 14:53:48 EST 2010

I'm trying to figure out a 32/64bit problem on OSX with the NAD files, and need some test points.

I found the example in the cs2cs man page, but it doesn't seem to agree with what I got with NADCON (http://www.ngs.noaa.gov/cgi-bin/nadcon.prl).  From NADCON, for the cs2cs example point -111.5 45.25919444444, I get a NAD83 to NAD27 latlong of 111d29'57.12835"w 45d15'33.35792"n.

I plug this into proj to get the UTM coordinate (this shouldn't be affected by NAD conversion in proj):

proj +proj=utm +zone=10 +ellps=GRS80
111d29'57.12835"w 45d15'33.35792"n
1402259.10	5076507.88

Not the same as the UTM coord from the cs2cs example:

cs2cs +proj=latlong +datum=NAD83 +to +proj=utm +zone=10 +datum=NAD27
-111.5 45.25919444444
1402285.99	5076292.42 -0.0

But, if I use NAD27 in proj on the NADCON latlong, I do get the UTM coord from the example, but this doesn't seem right - like I'm doing the datum conversion twice, once in NADCON latlong NAD83 to latlong NAD27, and once in proj latlong NAD?? to UTM NAD27:

proj +proj=utm +zone=10 +datum=NAD27
111d29'57.12835"w 45d15'33.35792"n
1402285.99	5076292.42

Is this right? does the output datum in proj also set the input latlong datum?

My own test with cs2cs (which I'm trying to figure out if it's wrong) gives:

1402224.58	5076275.42

Is maybe the cs2cs example wrong for the output?  I did figure out that the lat/long in the example should be switched (x,y order), so maybe something else is missing?

William Kyngesburye <kyngchaos*at*kyngchaos*dot*com>

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