[gdal-dev] gdal_contour out of memory

[Stefan Ziegler]

Hi

it seems that it has to do something with no-data areas. gdal_contour tries
to calculate all the contours from approx. 450m up to my no-data value
-3.4...e+38.

I use no gdal_fillnodata.py to fill the no data areas.

So I still think there is a slighly different behaviour of gdal since my
last calculations with the same commands and data with Ubuntu 10.04.

best regards
Stefan

On Thu, Apr 7, 2016 at 12:58 PM, Even Rouault <even.rouault at spatialys.com>
wrote:

> Stefan,
>
> > I have problems creating contours with gdal_contour and some tiff files.
> > The following command
> >
> > gdal_contour -i 1.0 6800_2480.tif out.shp
> >
> > ends with "0Killed" after eating all memory and all swap. It happens with
> > gdal 1.11 and gdal-master. It did work on a Ubuntu 10.04 machine (as far
> as
> > I remember). Now I'm on Ubuntu 14.04.
>
> Comparing the source code, the algorithm hasn't fundamentaly changed, at
> least
> since GDAL 1.5. I can reproduce your issue with latest trunk or 1.5.X.
> It is related to the fact that your source dataset has floating point
> values.
> An easy workaround is to translate your raster into a Int16 one and contour
> it. I've just tried it and it works.
> Or you could possibly round values to 0.5 precision with gdal_calc.py for
> perhaps a smoother result. But basically the contour alg seems to require a
> lot of memory if every pixel is different from its neighbour (might be an
> approximation of what happens as the algorithm is non trivial and I didn't
> study it in detail).
> It might be worth opening a ticket on that.
>
> Even
>
> >
> > Tiff file can be found here:
> > http://maps.zh.ch/download/hoehen/2014/dtm/tif/6800_2480.tif
> >
> > Any ideas?
> >
> > regards
> > Stefan
>
> --
> Spatialys - Geospatial professional services
> http://www.spatialys.com
>
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