2

I've downloaded several 7.5 minute DEM files from USGS and they have file names like:

1661629.DEM.SDTS.TAR

On MAC these decompress into a folder with serval files having the extension '.DDF'. Is there a shareware program that allows me to convert them to a basic ASCII text DEM file under the Mac OS X operating system?

3

GDAL is a free geospatial raster translation program that will convert USGS sdts dem to USGS asci dem. A Mac installer is available here gdal installers.

I'm unfamiliar with a Mac, but you will run gdal_translate.exe from a command line. Something like gdal_translate -of USGSDEM 1661629.DEM.SDTS. -of is the output format. The gdal_translate command help page is here translate These are gdal format abbreviations formats

  • thanks. I've downloaded but dont see a new Application. What exactly am I running! – Robert Sep 4 '13 at 20:55
  • I found the gdal_translate.exe which is installed under the /Library/Frameworks/ directory. After creating the ~/.bash_profile and adding the code below it runs from any directory:export PATH=/Library/Frameworks/GDAL.framework/Programs:$PATH I've managed to run the translator using Mac Terminal: gdal_translate -of USGSDEM 1663331.DEM.SDTS.TAR.GZ 1663331.DEM However, i get the error message below: ERROR 4: 1663331.DEM.SDTS.TAR.GZ' not recognised as a supported file format. Am I wrong in thinking it will read the compressed file? What should it be? – Robert Sep 5 '13 at 3:38
  • @robertprince-wright - Either uncompress or use the special GDAL "/vsitar" virtual filesystem syntax, i.e. gdal_translate -of USGSDEM /vsitar/1663331.DEM.SDTS.TAR.GZ 1663331.DEM – user2856 Sep 5 '13 at 4:54
  • @Luke - thanks, I've uncompressed the files and you end up with about 20 files with the DDL extension. I tried running 'gdal_translate' using the folder name but that fails too. So is there a specific file I need to point to? – Robert Sep 5 '13 at 13:21
  • My problem is solved by uncompressing the file and then pointing to the file containing 'CATD'. I presume it has special pointers to the other files. – Robert Sep 5 '13 at 17:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.