Given an unique raster topographic file at start, I want to get vector polygons for elevations thresholds 1m, 200m, 500m, 1000m, 2000m into a single shp file. I first slice my raster into 5 (or more) rasters, then polygonize each, and then have to merge them.
How to get these outputs into a single shape file ? Either by sending them as layers directly into the same file, or by creating individual shp files to merge into one final shp.
Current workflow details: It seems I must do this because poligonize works on pixels with a same value (elevation) x.
1. Generate raster slices: I used gdal_calc.py to generate kinds of vertical slices, with one .tif for each level :
gdal_calc.py -A crop.tif --outfile=level001.tif --calc="1*(A>0)" --NoDataValue=0 gdal_calc.py -A crop.tif --outfile=level200.tif --calc="200*(A>200)" --NoDataValue=0 ... ... ... ...
All conserved pixels in
level001.tif have an elevation of 1. All conserved pixels in
level200.tif have an elevation of 200m. Opened together in QGis it give slices like this:
2. Polygonize my rasters slices (files):
I run polygonize.py separatedly on each of these several raster files to get my vector layers:
gdal_polygonize.py level001.tif -f "ESRI Shapefile" levels001.shp levels001 elev gdal_polygonize.py level200.tif -f "ESRI Shapefile" levels200.shp levels200 elev ... ... ... ...
3. Merge into one shp file.
How to merge these shp outputs ?
Alternatively, I'am also interested by smoother workflow (loop).