[GRASS-user] Problem reprojecting to UTM 34 S

Fri May 16 04:03:14 EDT 2008

On Thu, May 15, 2008 at 8:01 PM, Tom Russo <russo at bogodyn.org> wrote:
> 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.

OK - I think we are getting somewhere.

>
>> >> 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.

Right - sorry.

>
>> >> 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?

No - just checked it and see below.

>
> 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

Here are the results as suggested:

~/> gdalwarp -s_srs '+proj=longlat +ellps=D_Clarke_1866 +no_defs'
-t_srs '+proj=utm +zone=34 +south +ellps=WGS84 +datum=WGS84 +
units=m +no_defs' hak_ser2.asc hak_ser2_utm34.asc
Processing input file hak_ser2.asc.
Using internal nodata values (eg. -9999) for image hak_ser2.asc.
0...10...20...30...40...50...60...70...80...90...100 - done.

~/> 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"]]
Origin = (-17471.391705359546904,-2431926.174459759611636)
Pixel Size = (1715.270741799227608,-1715.270741799227608)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (  -17471.392,-2431926.174) ( 15d59'39.65"E, 21d54'55.81"S)
Lower Left  (  -17471.392,-3941364.427) ( 15d17'55.27"E, 35d28'51.77"S)
Upper Right ( 1745826.931,-2431926.174) ( 32d58'5.17"E, 21d33'19.99"S)
Lower Right ( 1745826.931,-3941364.427) ( 34d34'59.95"E, 34d50'47.92"S)
Center      (  864177.770,-3186645.301) ( 24d43'43.82"E, 28d45'21.15"S)
Band 1 Block=1028x1 Type=Float32, ColorInterp=Gray
>

>
> 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?

GDAL 1.5.0, released 2007/12/18

>
> --
> 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
>
>

-- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology, UCT), Dipl. Phys. (Germany)

Plant Conservation Unit
Department of Botany
University of Cape Town
Rondebosch 7701
South Africa