update examples with graticule, change default lon_step=45 (#369)

README.md

@@ -168,7 +168,7 @@ plotter.add_mesh(
 )
 plotter.add_base_layer(texture=gv.natural_earth_hypsometric())
 plotter.add_coastlines(resolution="10m")
-plotter.add_graticule(lon_step=45)
+plotter.add_graticule()
 plotter.view_xy(negative=True)
 plotter.add_axes()
 plotter.show()
@@ -260,7 +260,7 @@ sargs = {"title": f"{sample.name} / {sample.units}"}
 plotter.add_mesh(mesh, scalar_bar_args=sargs)
 plotter.add_coastlines()
 plotter.add_base_layer(texture=gv.natural_earth_hypsometric())
-plotter.add_graticule(lon_step=45)
+plotter.add_graticule()
 plotter.add_axes()
 plotter.view_xy()
 plotter.show()
@@ -304,7 +304,7 @@ sargs = {"title": f"{sample.name} / {sample.units}"}
 plotter.add_mesh(mesh, scalar_bar_args=sargs)
 plotter.add_coastlines()
 plotter.add_base_layer(texture=gv.natural_earth_hypsometric())
-plotter.add_graticule(lon_step=45)
+plotter.add_graticule()
 plotter.add_axes()
 plotter.view_xy()
 plotter.show()

src/geovista/examples/from_unstructured__icosahedral.py

@@ -23,7 +23,7 @@ def main() -> None:
     Circulation Model (GCM) part of Institut Pierre-Simon Laplace (IPSL-CM) Earth
     System Model. The data targets the mesh faces/cells.
 
-    Note that, Natural Earth coastlines are also rendered.
+    Note that, a graticule and Natural Earth coastlines are also rendered.
 
     """
     # load the sample data
@@ -40,6 +40,7 @@ def main() -> None:
     sargs = {"title": f"{sample.name} / {sample.units}", "shadow": True}
     plotter.add_mesh(mesh, scalar_bar_args=sargs)
     plotter.add_coastlines()
+    plotter.add_graticule()
     plotter.add_axes()
     plotter.add_text(
         "DYNAMICO Icosahedral (10m Coastlines)",

src/geovista/examples/from_unstructured__icosahedral_poly.py

@@ -23,8 +23,8 @@ def main() -> None:
     Circulation Model (GCM) part of Institut Pierre-Simon Laplace (IPSL-CM) Earth
     System Model. The data targets the mesh faces/cells.
 
-    Note that, Natural Earth coastlines are also rendered, and the mesh is transformed
-    to the Polyconic pseudo-conical projection.
+    Note that, a graticule and Natural Earth coastlines are rendered, and the
+    mesh is also transformed to the Polyconic pseudo-conical projection.
 
     """
     # load the sample data
@@ -41,6 +41,7 @@ def main() -> None:
     sargs = {"title": f"{sample.name} / {sample.units}", "shadow": True}
     plotter.add_mesh(mesh, scalar_bar_args=sargs)
     plotter.add_coastlines()
+    plotter.add_graticule()
     plotter.add_axes()
     plotter.add_text(
         f"DYNAMICO Icosahedral ({projection})",

src/geovista/examples/from_unstructured__lfric_sst.py

@@ -22,8 +22,8 @@ def main() -> None:
     It uses an unstructured Met Office LFRic C48 cubed-sphere of surface temperature
     data located on the mesh faces/cells.
 
-    Note that, a threshold is also applied to remove land NaN cells, and a
-    Natural Earth base layer is rendered along with Natural Earth coastlines.
+    Note that, a threshold is also applied to remove land NaN cells. A Natural Earth
+    base layer is also rendered along with Natural Earth coastlines and a graticule.
 
     """
     # load the sample data
@@ -49,6 +49,7 @@ def main() -> None:
     plotter.add_mesh(mesh, show_edges=True, scalar_bar_args=sargs)
     plotter.add_base_layer(texture=gv.natural_earth_1())
     plotter.add_coastlines()
+    plotter.add_graticule()
     plotter.add_axes()
     plotter.add_text(
         "LFRic C48 Unstructured Cube-Sphere (10m Coastlines)",

src/geovista/examples/from_unstructured__lfric_sst_bonne.py

@@ -22,9 +22,9 @@ def main() -> None:
     It uses an unstructured Met Office LFRic C48 cubed-sphere of surface temperature
     data located on the mesh faces/cells.
 
-    Note that, a threshold is also applied to remove land NaN cells, and a
-    Natural Earth base layer is rendered along with Natural Earth coastlines. The mesh
-    is also transformed to the Bonne projection.
+    Note that, a threshold is also applied to remove land NaN cells. A Natural Earth
+    base layer is also rendered along with Natural Earth coastlines and a graticule.
+    The mesh is also transformed to the Bonne projection.
 
     """
     # load the sample data
@@ -45,11 +45,12 @@ def main() -> None:
     mesh = mesh.threshold()
 
     # plot the mesh
-    plotter = gv.GeoPlotter(crs=(projection := "+proj=bonne +lat_1=10"))
+    plotter = gv.GeoPlotter(crs=(projection := "+proj=bonne +lat_1=10 +lon_0=180"))
     sargs = {"title": f"{sample.name} / {sample.units}", "shadow": True}
     plotter.add_mesh(mesh, show_edges=True, scalar_bar_args=sargs)
     plotter.add_base_layer(texture=gv.natural_earth_1())
     plotter.add_coastlines()
+    plotter.add_graticule()
     plotter.add_axes()
     plotter.add_text(
         f"LFRic C48 Unstructured Cube-Sphere ({projection})",

src/geovista/gridlines.py

@@ -82,7 +82,7 @@
 LONGITUDE_START: float = BASE
 
 #: The default step size between graticule meridians (degrees).
-LONGITUDE_STEP: float = 30.0
+LONGITUDE_STEP: float = 45.0
 
 #: The period or upper bound (degrees) for meridian step size.
 LONGITUDE_STEP_PERIOD: float = 180.0