add tests for area and area density layout

atlite/cutout.py

@@ -574,14 +574,15 @@ def area(self, crs=3035):
         Parameters
         ----------
         crs : int, optional
-            CRS to calculate the total area of grid cells in m^2.
-            The default is 3035 which is suitable for the European area.
+            The coordinate reference system (CRS) to use for the calculation.
+            The default value is 3035, which is a suitable projection for Europe and returns the area in square meters.
 
         Returns
         -------
-        None.
+        xr.DataArray
+            A DataArray containing the area per grid cell with coordinates (x,y).
         """
-        area = self.grid.to_crs(crs).area.div(1e6)
+        area = self.grid.to_crs(crs).area
         return xr.DataArray(
             area.values.reshape(self.shape),
             [self.coords["y"], self.coords["x"]],
@@ -660,7 +661,7 @@ def layout_from_area_density(self, capacity_density, crs=3035):
             capacity placed within one grid cell.
         """
 
-        return capacity_density * self.area(crs)
+        return capacity_density * self.area(crs) / 1e6
 
     availabilitymatrix = compute_availabilitymatrix
 

test/test_creation.py

@@ -114,3 +114,11 @@ def test_sel(ref):
     cutout = ref.sel(x=slice(X0 + 2, X1 - 1), y=slice(Y0 + 1, Y1 - 2))
     assert cutout.coords["x"][0] - ref.coords["x"][0] == 2
     assert cutout.coords["y"][-1] - ref.coords["y"][-1] == -2
+
+
+def test_layout_from_area_density(ref):
+    density = 0.1
+    layout = ref.layout_from_area_density(density)
+    assert layout.dims == ("y", "x")
+    assert layout.shape == (ref.data.y.size, ref.data.x.size)
+    assert ref.area().sum() * density / 1e6 == layout.sum()

test/test_gis.py

@@ -200,6 +200,21 @@ def test_open_closed_checks(ref, geometry, raster):
     assert not excluder.all_closed and excluder.all_open
 
 
+def test_area(ref):
+    """
+    Test the area of the cutout.
+    """
+    area = ref.area()
+    assert isinstance(area, xr.DataArray)
+    assert area.dims == ("y", "x")
+
+    # now test with a different crs
+    with pytest.warns(UserWarning):
+        assert ref.area(crs=ref.crs).sum().item() == (X1 - X0 + ref.dx) * (
+            Y1 - Y0 + ref.dy
+        )
+
+
 def test_transform():
     """
     Test the affine transform.