Use CDO function proj_lonlat_to_lcc() to convert lonlat to lcc coordinates.

src/grid.c

@@ -21,6 +21,7 @@
 #include "vlist.h"
 
 double grid_missval = -9999.;
+int (*proj_lonlat_to_lcc_func)() = NULL;
 
 /* the value in the second pair of brackets must match the length of
  * the longest string (including terminating NUL) */
@@ -3627,10 +3628,10 @@ void gridDefParamLCC(int gridID, double missval, double lon_0, double lat_0, dou
   cdiDefAttFlt(gridID, CDI_GLOBAL, "latitude_of_projection_origin", CDI_DATATYPE_FLT64, 1, &lat_2);
   if ( a > 0 ) cdiDefAttFlt(gridID, CDI_GLOBAL, "earth_radius", CDI_DATATYPE_FLT64, 1, &a);
   if ( rf > 0 ) cdiDefAttFlt(gridID, CDI_GLOBAL, "inverse_flattening", CDI_DATATYPE_FLT64, 1, &rf);
-  if ( IS_NOT_EQUAL(xval_0, missval) ) cdiDefAttFlt(gridID, CDI_GLOBAL, "longitudeOfFirstGridPointInDegrees", CDI_DATATYPE_FLT64, 1, &xval_0);
-  if ( IS_NOT_EQUAL(yval_0, missval) ) cdiDefAttFlt(gridID, CDI_GLOBAL, "latitudeOfFirstGridPointInDegrees", CDI_DATATYPE_FLT64, 1, &yval_0);
   if ( IS_NOT_EQUAL(x_0, missval) ) cdiDefAttFlt(gridID, CDI_GLOBAL, "false_easting", CDI_DATATYPE_FLT64, 1, &x_0);
   if ( IS_NOT_EQUAL(y_0, missval) ) cdiDefAttFlt(gridID, CDI_GLOBAL, "false_northing", CDI_DATATYPE_FLT64, 1, &y_0);
+  if ( IS_NOT_EQUAL(xval_0, missval) ) cdiDefAttFlt(gridID, CDI_GLOBAL, "longitudeOfFirstGridPointInDegrees", CDI_DATATYPE_FLT64, 1, &xval_0);
+  if ( IS_NOT_EQUAL(yval_0, missval) ) cdiDefAttFlt(gridID, CDI_GLOBAL, "latitudeOfFirstGridPointInDegrees", CDI_DATATYPE_FLT64, 1, &yval_0);
 
   grid_t *gridptr = grid_to_pointer(gridID);
   gridptr->projtype = CDI_PROJ_LCC;

src/grid.h

@@ -7,6 +7,7 @@
 #include "cdi_att.h"
 
 extern double grid_missval;
+extern int (*proj_lonlat_to_lcc_func)();
 
 typedef unsigned char mask_t;
 

src/stream_cgribex.c

@@ -406,6 +406,14 @@ void cgribexAddRecord(stream_t * streamptr, int param, int *isec1, int *isec2, d
           double lat_0 = lat_2;
           double x_0 = grid_missval;
           double y_0 = grid_missval;
+
+          if ( proj_lonlat_to_lcc_func )
+            {
+              x_0 = xval_0; y_0 = yval_0;
+              proj_lonlat_to_lcc_func(grid_missval, lon_0, lat_0, lat_1, lat_2, a, rf, 1, &x_0, &y_0);
+              if ( IS_NOT_EQUAL(x_0, grid_missval) && IS_NOT_EQUAL(y_0, grid_missval) )
+                { x_0 = -x_0; y_0 = -y_0; }
+            }
           gridDefParamLCC(gridID, grid_missval, lon_0, lat_0, lat_1, lat_2, a, rf, xval_0, yval_0, x_0, y_0);
         }
     }

src/stream_gribapi.c

@@ -492,7 +492,7 @@ void gribapiAddRecord(stream_t * streamptr, int param, grib_handle *gh,
       long earthIsOblate;
       grib_get_long(gh, "earthIsOblate", &earthIsOblate);
       if ( earthIsOblate ) { a = 6378160.; rf = 297.0; }
-      double lon_0, lat_0, lat_1, lat_2, xval_0, yval_0, x_0 = grid_missval, y_0 = grid_missval;
+      double lon_0, lat_1, lat_2, xval_0, yval_0;
       long projflag = 0;
       grib_get_double(gh, "longitudeOfFirstGridPointInDegrees", &xval_0);
       grib_get_double(gh, "latitudeOfFirstGridPointInDegrees", &yval_0);
@@ -503,7 +503,17 @@ void gribapiAddRecord(stream_t * streamptr, int param, grib_handle *gh,
       bool lsouth = gribbyte_get_bit(projflag, 1);
       if ( lsouth ) { lat_1 = -lat_1; lat_2 = -lat_2; }
 
-      lat_0  = lat_2;
+      double lat_0 = lat_2;
+      double x_0 = grid_missval;
+      double y_0 = grid_missval;
+
+      if ( proj_lonlat_to_lcc_func )
+        {
+          x_0 = xval_0; y_0 = yval_0;
+          proj_lonlat_to_lcc_func(grid_missval, lon_0, lat_0, lat_1, lat_2, a, rf, 1, &x_0, &y_0);
+          if ( IS_NOT_EQUAL(x_0, grid_missval) && IS_NOT_EQUAL(y_0, grid_missval) )
+            { x_0 = -x_0; y_0 = -y_0; }
+        }
       gridDefParamLCC(gridID, grid_missval, lon_0, lat_0, lat_1, lat_2, a, rf, xval_0, yval_0, x_0, y_0);
     }