[GRASS-user] Problem reprojecting to UTM 34 S

[Tom Russo]

On Thu, May 15, 2008 at 06:16:34PM +0200, we recorded a bogon-computron collision of the <r.m.krug at gmail.com> flavor, containing:
> On Thu, May 15, 2008 at 4:46 PM, Michael Perdue <michael_perdue at yahoo.ca> wrote:
> > From what I see, gdalinfo hak_ser2.asc is listing all the latitudes as being
> > positive which means that they are in the northern hemisphere. It looks to
> > me like gdal is doing the right thing and there is something wrong with the
> > ASCII grid.

That's not how I read it.  The upper left corner is 
> >> Upper Left  (  15.9916667, -21.9918333)

which is 15.9916667 East longitude and 21.9918333 South latitude.

> >> I have a ESRI asc raster in +proj=longlat +ellps=D_Clarke_1866 +no_defs
[...]
> >>
> >> gdalwarp -s_srs '+proj=longlat +ellps=D_Clarke_1866 +no_defs' -t_srs
> >> EPSG:32734 hak_ser2.asc hak_ser2_utm34.asc
> >>
> >> where EPSG:323734 is the definition for UTM 34 S WGS 84

I assume you mean "32734" not "323734" --- 32734 is WGS84 Zone 34 southern
hemisphere.

> >> But I get:
> >>
> >> rkrug at ecolmod1:~/Documents/Projects/AlienSpread/GIS.local/Rainer_subset>
> >> gdalinfo hak_ser2_utm34.asc
> >> Driver: GTiff/GeoTIFF
> >> Files: hak_ser2_utm34.asc
> >> Size is 1028, 880
> >> Coordinate System is:
> >> PROJCS["WGS 84 / UTM zone 34N",
> >>   GEOGCS["WGS 84",
> >>       DATUM["WGS_1984",
> >>           SPHEROID["WGS 84",6378137,298.2572235629972,
> >>               AUTHORITY["EPSG","7030"]],
> >>           AUTHORITY["EPSG","6326"]],
> >>       PRIMEM["Greenwich",0],
> >>       UNIT["degree",0.0174532925199433],
> >>       AUTHORITY["EPSG","4326"]],
> >>   PROJECTION["Transverse_Mercator"],
> >>   PARAMETER["latitude_of_origin",0],
> >>   PARAMETER["central_meridian",21],
> >>   PARAMETER["scale_factor",0.9996],
> >>   PARAMETER["false_easting",500000],
> >>   PARAMETER["false_northing",0],
> >>   UNIT["metre",1,
> >>       AUTHORITY["EPSG","9001"]],
> >>   AUTHORITY["EPSG","32634"]]

That's odd --- you say you used "EPSG:32734" but this last line clearly
shows "32634" (which is WGS 84 zone 34 Northern hemisphere).  Is it
possible you fat-fingered when typing in the command line?

If not, maybe you could try using the PROJ.4 specification for the
coordinate system for -t_srs instead of the EPSG number?

 gdalwarp -t_srs '+proj=utm +zone=34 +south +ellps=WGS84 +datum=WGS84 +units=m +no_defs' -s_srs '+proj=longlat +ellps=D_Clarke_1866 +no_defs' hak_ser2.asc hak_ser2_utm34.asc

If that works, then perhaps there's something goofy with how GDAL is processing
your EPSG number (maybe leaving off the "+south" when it creates the proj.4
arguments?).  What version of GDAL are you using?

-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236 AHTB#1 http://kevan.org/brain.cgi?DDTNM
 "It's so simple to be wise: just think of something stupid to say and
  then don't say it."  --- Sam Levinson