Given a topographic GIS raster of one country:
Given an elevation threshold n = 50 (meters)
How to polygonize pixels when z >= n ?
gdal_polygonize.py is not clear on this point. It states
This utility creates vector polygons for all connected regions of pixels in the raster sharing a common pixel value. So I guess it MUST be like
z = something and only this. I don't understand where to state the condition.
Current workflow details:
# download: curl -o ETOPO1.zip 'http://www.ngdc.noaa.gov/mgg/global/relief/ETOPO1/data/ice_surface/grid_registered/georeferenced_tiff/ETOPO1_Ice_g_geotiff.zip' # unzip: unzip ETOPO1.zip # crop: gdal_translate -projwin -005.50 051.30 10.00 041.00 ETOPO1_Ice_g_geotiff.tif crop.tif