update README + BE Ardenne coordinates

utils/generate-tiles-list.py

@@ -16,8 +16,16 @@ max_y = 50.184
 min_x = 5.735
 min_y = 49.452
 
+# BE ardenne coordinates
+
+max_x = 6.40
+max_y = 50.77
+min_x = 4.13
+min_y = 49.49
+
+
 min_z = 9
-max_z = 17
+max_z = 18
 
 for z in range(min_z, max_z+1):
     x1_tile, y1_tile = deg2num(max_y, max_x, z)