<html>
GRASS 5.0.0 pre4 (and probably earlier) was "hardwired" to read
the state27 definitions when you created a new location. I don't know if
this has been fixed. Eric Miller suggested renaming you
grass5/etc/state27 file and the creating a symbolic link to the
state27->state83 so that when you created a new location it would read
the values from state83. So you might look in your PROJ_INFO files and
see what values got used.<br><br>
Also - I don't think datum transformations are supported. Somebody please
correct me if I'm wrong. In my area (western wyoming) there is only about
1 second of rotation between NAD27 and NAD83 so I have been able to
manually edit the headers for raster files and get a workable datum
conversion for a small area (a DRG).<br><br>
Rich<br><br>
At 05:42 PM 11/25/2002 -0500, you wrote:<br>
<blockquote type=cite class=cite cite><font face="arial" size=2>Grass
5.0.0</font><br>
<font face="arial" size=2>spar-sun-solaris2.7</font><br>
<br>
<font face="arial" size=2>I am having trouble projecting vector data to a
new projection/datum.</font><br>
<font face="arial" size=2>I have North Carolina state plane (NCSP) NAD83
Meters raster aerial photo data.</font><br>
<font face="arial" size=2>I have NCSP NAD83 Feet road data. I v.proj the
road data and it appears fine.</font><br>
<font face="arial" size=2>(The roads overlay the roads on the
raster.)</font><br>
<br>
<font face="arial" size=2>I have NCSP NAD27 feet data of Cadastral
(Property). When I v.proj this data to </font><br>
<font face="arial" size=2>NCSP NAD83 Meters, it appears about 9700 Meters
west of the NAD83 data (using</font><br>
<font face="arial" size=2>d.measure). When I v.proj UTM zone 18
NAD27 Meters Hydrography data, it appears</font><br>
<font face="arial" size=2>at the same relative position as the other
NAD27 data (the Cadastral data).</font><br>
<br>
<font face="arial" size=2>In other words, the NAD83 data lines up. The
NAD27 data lines up with NAD27 data.</font><br>
<font face="arial" size=2>But NAD27 does not line up with NAD
83.</font><br>
<br>
<font face="arial" size=2>It looks like the projection is occurring
correctly but the datum transformation is not.</font><br>
<br>
<font face="arial" size=2>I have carefully set up the proj_info and
proj_units files. I even copied over Eric Miller's</font><br>
<font face="arial" size=2>state plane files and tried those. Same
results. (see
<a href="http://pweb.jps.net/~egm2/grass/STP/index.html">http://pweb.jps.net/~egm2/grass/STP/index.html</a>)</font><br>
<br>
<font face="arial" size=2>The difference is suspiciously similar to the
difference in false easting between NCSP NAD83 and </font><br>
<font face="arial" size=2>NCSP NAD27. </font><br>
<br>
<font face="arial" size=2>Projecting from the NAD83 M to NAD27 Ft (the
reverse of above) gives similar results</font><br>
<font face="arial" size=2>with the NAD83 data appearing 9700 meters east
of the NAD27 data</font><br>
<br>
<font face="arial" size=2>Am I doing something wrong? Has anyone
else had a similar problem?</font><br>
<br>
<font face="arial" size=2>John Gillette</font><br>
<br>
</blockquote>
<x-sigsep><p></x-sigsep>
<br>
Richard W. Greenwood, PLS<br>
Greenwood Mapping, Inc.<br>
Rich@GreenwoodMap.com<br>
(307) 733-0203<br>
<a href="http://www.greenwoodmap.com/" eudora="autourl">http://www.GreenwoodMap.com</a></html>