[GRASSLIST:4231] Re: NAD27 vs NAD83 SDTS files

[Eric G. Miller]

On Tue, Aug 06, 2002 at 12:08:26PM -0800, Victor Wren wrote:
> > 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).

You'll have to import them into an appropriately defined mapset and then
project them (v.proj or r.proj).  Never heard of NAD88, but there are
quite a few adjustments (such as HARN), so I wouldn't reject it out of
hand...

-- 
Eric G. Miller <egm2 at jps.net>