Add BIGTIFF IFSAFER for DEM generation

opendm/dem/utils.py

@@ -5,5 +5,6 @@ def get_dem_vars(args):
         'COMPRESS': 'LZW',
         'BLOCKXSIZE': 512,
         'BLOCKYSIZE': 512,
+        'BIGTIFF': 'IF_SAFER',
         'NUM_THREADS': args.max_concurrency,
     }