Filling of nodata values for dem.tif now works as intended.

There is a bug in gdal_grid 1.11.2 that we are using that does not handle
nodata flag properly. Thus this workaround was used to set nodata properly.

dvlp/grid_tile.sh

@@ -307,13 +307,16 @@ fi
 gdalwarp roofs.tif roofs_corr.tif
 
 # interpolate raster from dem points
-if [ ! -f dem.tif ]; then
-    grid_shape  $DEM_POINTS_OUTSIDE_BUILDINGS_SHAPE dem.tif $x1 $y1 $x2 $y2 $ncells "invdistnn:radius=100:max_points=2"
-    gdal_fillnodata.py -md 2000 dem.tif
+if [ ! -f dem_filled.tif ]; then
+    grid_shape  $DEM_POINTS_OUTSIDE_BUILDINGS_SHAPE dem.tif $x1 $y1 $x2 $y2 $ncells "invdistnn:radius=100:max_points=2:nodata=-9999"
+    # Since we use a old gdal_grid that does not set nodata flag properly, we must call gdal_translate first before
+    # gdal_fillnodata.py can be used.
+    gdal_translate -a_nodata -9999 dem.tif dem_nodata_set.tif
+    gdal_fillnodata.py -md 2000 dem_nodata_set.tif dem_filled.tif
 fi
 
 # fix for bug in gdal_grid causing rasters with strange orientation, that cannot be handled by gdal_calc.py
-gdalwarp dem.tif $dem
+gdalwarp dem_filled.tif $dem
 
 gdal_rasterize -te $x1 $y1 $x2 $y2 -ts $ncells $ncells  -init 0 -burn 1 -a_nodata -9999  -l buildings db.sqlite building_mask.tif