last fixes

- comments onno
- new link with info on EPSG 28992
- add trap for duplicate indices in gdf_to_grid (better error message for users)

nlmod/dims/grid.py

@@ -1706,6 +1706,9 @@ def gdf_to_grid(
     if ml is None and ix is None:
         raise (ValueError("Either specify ml or ix"))
 
+    if gdf.index.has_duplicates or gdf.columns.has_duplicates:
+        raise ValueError("gdf should not have duplicate columns or index.")
+
     if ml is not None:
         if isinstance(ml, xr.Dataset):
             ds = ml

nlmod/epsg28992.py

@@ -1,8 +1,10 @@
 """
-NOTE: this is the correct epsg:28992 definition for plotting backgroundmaps in RD
-More info (in Dutch) here:
-https://qgis.nl/2011/12/05/epsg28992-of-rijksdriehoekstelsel-verschuiving/
-This was still a problem in October 2023
+NOTE: this is the correct epsg:28992 definition for plotting backgroundmaps in RD.
+
+Related information (in Dutch):
+https://geoforum.nl/t/betrouwbare-bron-voor-proj4-definitie-van-rd-new-epsg-28992/5144/15
+This was still a problem in July 2024.
+
 """
 
 EPSG_28992 = (

nlmod/plot/__init__.py

@@ -8,7 +8,7 @@
     geotop_lithok_in_cross_section,
     geotop_lithok_on_map,
     map_array,
-    # modelextent,
+    modelextent,
     modelgrid,
     surface_water,
 )