[Gdal-dev] Python USGS ASCII DEM

Norman Barker normanb at comsine.co.uk
Mon Jul 26 14:43:47 EDT 2004


We are writing an GDAL program using the python wrappers and everything 
is going well (the wrappers
around GDAL are really cool!). 

I am having problems with a bottleneck with the USGS ASCII DEMs that we 
are using.  I understand from
http://www.remotesensing.org/gdal/frmt_usgsdem.html that they are 
treated as one tile and are thus loaded in

The line we are using is
        dem_src_data = dem_band.ReadAsArray(0, (start_row + iY) , 
src_tif.RasterXSize, 1)
so we are trying to read a section as long as the input tif file from 
the DEM.  The DEMS are over 100mb.

All the other code is very fast thanks to GDAL, but is there a work 
around for this bottle neck?

Many thanks,


Norman Barker
Software Engineer
ComSine Ltd
Tel: +44 (0)1483 457121
Web: http://www.comsine.com
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