[gdal-dev] Question on gdal_contour and limiting the range of contours generated.

[jratike80]

Hi,

I believe I would use gdal_calc https://gdal.org/programs/gdal_calc.html and
make the terrain above the sea level flat before creating the contours. And
I would avoid shapefiles and use GeoPackage as output format. 

There is a button "Edit on GitHub" in the top-right corner on page
https://gdal.org/programs/gdal_contour.html, feel free to test it.

-Jukka Rahkonen-



Stephen Woodbridge-4 wrote
> Hi,
> 
> I want to use gdal_contour to generate shapefile contours which is 
> pretty straight forward except I'm working with coastal relief data that 
> has both elevation and bathymetry. I only want contours for the
> bathymetry.
> 
> I tried setting the -off -5 and -i -5 with the idea that this would 
> start me at a depth of -5 and generate contours every -5 units deeper, 
> but the generated an empty files. Seems like -i parameter can not be 
> negative (should be mentioned in the docs).
> 
> This sets the depth to 400ft and generates contours every 5 ft above that:
> 
> gdal_contour -off -121.92 -i 1.524 bathy-value/crm_vol2.nc.tif 
> bathy-contours/crm_vol2.nc-5.shp
> 
> How can I stop/limit the process and stop at 0 (ie: sea level)? I don't 
> want land elevation contours. Like a -limit 0 argument?
> 
> If this can't be done, it would be a nice option to have so you can 
> breakup contours into multiple shapefiles to avoid overflowing them
> 
> Thanks,
>    -Steve





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