[GRASSLIST:4227] Re: NAD27 vs NAD83 SDTS files

Victor Wren vwren at timension.com
Tue Aug 6 16:08:26 EDT 2002

> Well, it is peculiar.  I suspect the problem is with the SDTS files
> themselves.  As a note, r.in.gdal and v.in.sdts use different code
> for reading SDTS files.  Also, neither does projection on import.
> Perhaps you have a mix of NAD27 and NAD83 quads?  You can examine the
> SDTS files with m.sdts.read (see the ****XREF.DDF file; NAS is NAD27,
> NAR is NAD83).

Bingo!  (You can also examine the metadata with the free DLG viewer 
from the USGS).  As it turns out, all of my DEM SDTS files are 
NAD27, but I had the mapset set up for NAD83, and some of the 
vector files are NAD83 (our contractors are claiming they're working in 
NAD88, but I'm not going to get into that).  Now another question -- 
how can I bring an NAD27 vector map into an NAD83 mapset?  Or 
alternatively, how do I convert a binary raster that is in NAD27 to 
NAD83?  The only thing I can think of right now is exporting across 
mapsets (like exporting [importing?] dem at OTHERSET using r.proj or 
some such).

Thanks  much for your help!

Victor Wren
Timension Inc.
1350 C Pear Ave
Mountain View CA 94043
(650) 564-9397
Fax: (650) 564-9398
Opinions stated in this letter are not necessarily
those of Timension Inc. or the management.  All
Rights Reserved.  No spitting.

More information about the grass-user mailing list