[gdal-dev] Ruby bindings and geotiff...

[Adam Fowler]

Hi All,

I'm trying to write a Ruby app to read the new and fantastic NASA
ASTER Elevation DEM. This is of course in GeoTiff format.

I'm wondering if anyone has examples in any language of using GDAL to
read a particular location's data from a geotiff file? I can do the
calculations to figure out which of the 3601x3601 data elements I need
to read is, but I can't find an example of using GDAL to load only
that pixel's information.

If anyone has an example that would be great.

I'm also having issues installing GDAL on OS X even when using
macports. I can build and install fine without the ruby bindings, but
using them (via editing the port file to include --with-ruby) gives
me:

libtool: link: /usr/bin/g++-4.0 gdal_wrap.o -o gdal.so
-L/opt/local/lib
-L/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib
-L/opt/local -L/usr/X11/lib
-L/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_ports_science_gdal/work/gdal-1.6.0
/opt/local/lib/libgdal.dylib /opt/local/lib/libproj.dylib -lm
/opt/local/lib/libgif.dylib /opt/local/lib/libSM.dylib
/opt/local/lib/libICE.dylib /opt/local/lib/libX11.dylib
/opt/local/lib/libXau.dylib /opt/local/lib/libXdmcp.dylib -lgeotiff
/opt/local/lib/libtiff.dylib /opt/local/lib/libjpeg.dylib -lc
/opt/local/lib/libpng12.dylib -lz -ldl -lruby
Undefined symbols:
 "_main", referenced from:
    start in crt1.10.5.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
make[3]: *** [gdal.so] Error 1
make[2]: *** [build] Error 2
make[1]: *** [build] Error 2
make: *** [swig-modules] Error 2

Error: Status 1 encountered during processing.

I'm assuming it can't find ruby to link to, but not quite sure how to
resolve this. Does --with-ruby have any extra undocumented options?

If I figure it out I'd be happy to add to the Ruby WIKI page - who
should I email to get access/contribute information?

Thanks in advance.

Regards,

Adam.