[Proj] WGS84 to NAD27 latlong

[Frank Warmerdam]

Harry G McGavran Jr wrote:
> I have a newbie question -- with cs2cs should
> 
> cs2cs -f "%.12f" +proj=latlong +datum=WGS84 +to +proj=latlong +datum=NAD27
> 
> translate WGS84 latitude and longitude to NAD27 latitude and longitude???
> 
> When I try this, I get the same output as input.  Specifically,
> I am passing decimal degress on input and am getting the same decimal
> degrees output -- no translation --... this is with 4.4.9, 4.5.0, and 4.6.0.

Harry,

Two likely problems:

1) You don't have the datum shift files for NAD27.  For instance, do you
have the file "conus" in /usr/local/share/proj or whereever the appropriate
location is on your system?

2) You have the datum shift files, but your point does not fall in the area
of any of them.  What is your point?

The FAQ should have some material on datum shifting and grid shift files.
Read it over and hopefully it will help.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org