gridGetPlanetRadius: read attribute earth_radius directly

src/mpim_grid/grid_proj.cc

@@ -610,22 +610,6 @@ cdo_proj_to_lonlat(char *proj_params, size_t nvals, double *xvals, double *yvals
 double
 gridGetPlanetRadius(int gridID)
 {
-  double planetRadius = 0.0;
-
-  auto gridtype = gridInqType(gridID);
-  auto projtype = (gridtype == GRID_PROJECTION) ? gridInqProjType(gridID) : -1;
-  if (projtype == CDI_PROJ_LCC)
-    {
-      CDI_GridProjParams gpp;
-      gridInqParamsLCC(gridID, &gpp);
-      if (IS_EQUAL(gpp.b, gpp.mv)) planetRadius = gpp.a;
-    }
-  else if (projtype == CDI_PROJ_STERE)
-    {
-      CDI_GridProjParams gpp;
-      gridInqParamsSTERE(gridID, &gpp);
-      if (IS_EQUAL(gpp.b, gpp.mv)) planetRadius = gpp.a;
-    }
-
-  return planetRadius;
+  double radius{ 0 };
+  return (CDI_NOERR == cdiInqAttFlt(gridID, CDI_GLOBAL, "earth_radius", 1, &radius) && radius > 1) ? radius : 0.0;
 }