1066 modelbuilder fix inexact latlon bbox (#1067)

* moved meshkernel bbox to separate function

* updated notebook with bbox function

dfm_tools/meshkernel_helpers.py

@@ -19,6 +19,7 @@
     "meshkernel_delete_withgdf",
     "meshkernel_get_illegalcells",
     "meshkernel_to_UgridDataset",
+    "meshkernel_get_bbox",
     "make_basegrid",
     "refine_basegrid",
     "generate_bndpli_cutland",
@@ -351,6 +352,26 @@ def refine_basegrid(mk, data_bathy_sel, min_edge_size):
     return mk
 
 
+def meshkernel_get_outer_xycoords(mk:meshkernel.MeshKernel):
+    mesh_bnds = mk.mesh2d_get_mesh_boundaries_as_polygons()
+    xcoords = mesh_bnds.x_coordinates
+    ycoords = mesh_bnds.y_coordinates
+    if mesh_bnds.geometry_separator in xcoords:
+        # TODO: would be nice to get only the outer xycoords instead
+        # or to have easier selection of outer xycoords
+        raise Exception('use meshkernel_get_outer_xycoords() on an uncut grid')
+    return xcoords, ycoords
+
+
+def meshkernel_get_bbox(mk:meshkernel.MeshKernel):
+    """
+    get the bbox of a meshkernel instance as (xmin, ymin, xmax, ymax)
+    """
+    xcoords, ycoords = meshkernel_get_outer_xycoords(mk)
+    bbox = (xcoords.min(), ycoords.min(), xcoords.max(), ycoords.max())
+    return bbox
+
+
 def generate_bndpli_cutland(mk:meshkernel.MeshKernel, res:str='f', min_area:float = 0, crs:(int,str) = None, buffer:float = 0):
     """
     Generate a boundary polyline from the meshkernel object and cut away the landward part.
@@ -375,15 +396,11 @@ def generate_bndpli_cutland(mk:meshkernel.MeshKernel, res:str='f', min_area:floa
         DESCRIPTION.
 
     """
-
-    mesh_bnds = mk.mesh2d_get_mesh_boundaries_as_polygons()
-    if mesh_bnds.geometry_separator in mesh_bnds.x_coordinates:
-        raise Exception('use dfmt.generate_bndpli_cutland() on an uncut grid')
-    mesh_bnds_xy = np.c_[mesh_bnds.x_coordinates,mesh_bnds.y_coordinates]
-
-    bbox = (mesh_bnds.x_coordinates.min(), mesh_bnds.y_coordinates.min(), mesh_bnds.x_coordinates.max(), mesh_bnds.y_coordinates.max())
+    bbox = meshkernel_get_bbox(mk)
     coastlines_gdf = get_coastlines_gdb(bbox=bbox, res=res, min_area=min_area, crs=crs)
 
+    xcoords,ycoords = meshkernel_get_outer_xycoords(mk)
+    mesh_bnds_xy = np.c_[xcoords,ycoords]
     meshbnd_ls = LineString(mesh_bnds_xy)
     coastlines_mp = MultiPolygon(coastlines_gdf.geometry.tolist())
     coastlines_mp = coastlines_mp.buffer(buffer)

docs/whats-new.md

@@ -7,6 +7,9 @@
 - replaced buffer and floor/ceil with copernicusmarine `coordinates_selection_method`, this deprecated the `buffer` argument for `dfmt.download_CMEMS()` [#1061](https://github.com/Deltares/dfm_tools/pull/1061)
 - inclusive selection of outside timesteps in `open_prepare_dataset()` and thus in `cmems_nc_to_bc()` in [#1062](https://github.com/Deltares/dfm_tools/pull/1062)
 
+### Fix
+- fixed inexact latlon bbox in modelbuilder with `dfmt.meshkernel_get_bbox()` in [#1067](https://github.com/Deltares/dfm_tools/pull/1067)
+
 
 ## 0.32.0 (2025-01-14)
 

tests/examples/preprocess_modelbuilder.py

@@ -16,7 +16,7 @@
 
 ## input
 model_name = 'Bonaire'
-dir_output = r'p:\11209231-003-bes-modellering\hydrodynamica\hackathon\preprocessing\ModelBuilderOutput_JV2'
+dir_output = f"{model_name}_model"
 path_style = 'windows' # windows / unix, making relative paths only works when path_style is equal to os
 overwrite = False # used for downloading of forcing data. Always set to True when changing the domain
 crs = 'EPSG:4326'

tests/test_meshkernel_helpers.py

@@ -307,6 +307,27 @@ def test_meshkernel_to_UgridDataset(tmp_path):
     assert "wgs84" in ds_out.variables
 
 
+@pytest.mark.unittest
+def test_meshkernel_get_bbox():
+    projection = ProjectionType.SPHERICAL
+
+    # create basegrid
+    lon_min, lon_max, lat_min, lat_max = -6, 2, 48.5, 51.2
+    dxy = 0.5
+    make_grid_parameters = MakeGridParameters(origin_x=lon_min,
+                                              origin_y=lat_min,
+                                              upper_right_x=lon_max,
+                                              upper_right_y=lat_max,
+                                              block_size_x=dxy,
+                                              block_size_y=dxy)
+    mk = MeshKernel(projection=projection)
+    mk.curvilinear_compute_rectangular_grid_on_extension(make_grid_parameters)
+    mk.curvilinear_convert_to_mesh2d() #convert to ugrid/mesh2d
+
+    bbox = dfmt.meshkernel_get_bbox(mk)
+    assert np.allclose(bbox, (-6.0, 48.5, 2.0, 51.40631301478466))
+
+
 @pytest.mark.unittest
 def test_generate_bndpli_cutland():
     # domain, resolution and expected values