fix for Basemap.pcolormesh 'ortho' projection

lib/mpl_toolkits/basemap/__init__.py

@@ -3426,6 +3426,27 @@ def pcolormesh(self,x,y,data,**kwargs):
         if the dimensions are the same, then the last row and column of data will be ignored.
         """
         ax, plt = self._ax_plt_from_kw(kwargs)
+        # fix for invalid grid points
+        if ((np.any(x > 1e20) or np.any (y > 1e20)) and
+            len(x.shape) == 2 and len(y.shape) == 2):
+            if not x.shape == y.shape:
+                raise Exception('pcolormesh: x and y need same dimension')
+            nx,ny = x.shape
+            if nx < data.shape[0] or ny < data.shape[1]:
+                raise Exception('pcolormesh: data dimension needs to be at least that of x and y.')
+            mask = (
+                (x[:-1,:-1] > 1e20) |
+                (x[1:,:-1] > 1e20) |
+                (x[:-1,1:] > 1e20) |
+                (x[1:,1:] > 1e20) |
+                (y[:-1,:-1] > 1e20) |
+                (y[1:,:-1] > 1e20) |
+                (y[:-1,1:] > 1e20) |
+                (y[1:,1:] > 1e20)
+                )
+            # we do not want to overwrite original array
+            data = data[:nx-1,:ny-1].copy()
+            data[mask] = np.nan
         self._save_use_hold(ax, kwargs)
         try:
             ret =  ax.pcolormesh(x,y,data,**kwargs)