[Mapserver-users] slightly ot: help with cs2cs syntax

[Dan Harris]

I'm trying to figure out how to convert various state plane coordinates 
into long/lat.  From what I can tell, other than moving to postgis, the 
only way I can do it ( and store the converted points ) is to call cs2cs 
from an app.

The problem I'm running into is that the coordinates returned to me are 
WAY off.. I must be doing something wrong but documentation examples are 
very scarce.  So as a test, I'm trying to convert a simple state plane 
into long/lat using the following:

cs2cs  +init=nad27:502 +to +proj=longlat -r -f "%.2f" << EOF
 > 2180318 686562
 > EOF
-104.30 57.11 0.00

The resulting latitude is nearly 20 degrees north of where it should be.. 

To make things even more interesting, if I take off the ending '8' from 
2180318, I get this:

 cs2cs  +init=nad27:502 +to +proj=longlat -r -f "%.2f" << EOF
 > 218031 686562
 > EOF
-104.60 39.79 0.00

I have no explanation why taking off the trailing non-decimal number 
from the X coord ( which should be completely invalid ) would give me 
closer results?

This is closer, but still not accurate in comparisons with MapInfo.  
MapInfo says it should be a -104.85, 39.71

Any ideas what I might be doing wrong here?  I'm sure the original 
coordinates are NAD27, Colorado Central.

Thank you!

-Dan