Mercator: implement nearest

definitions/grib1/grid_definition_1.def

@@ -64,6 +64,8 @@ iterator mercator(numberOfPoints,missingValue,values,
           jPointsAreConsecutive,
           alternativeRowScanning);
 
+nearest mercator(values,radius,Nx,Ny);
+
 meta latLonValues latlonvalues(values);
 alias latitudeLongitudeValues=latLonValues;
 meta latitudes latitudes(values,0);

definitions/grib2/template.3.10.def

@@ -75,6 +75,8 @@ iterator mercator(numberOfPoints,missingValue,values,
           iScansNegatively, jScansPositively,
           jPointsAreConsecutive, alternativeRowScanning);
 
+nearest mercator(values,radius,Nx,Ny);
+
 meta latLonValues latlonvalues(values);
 alias latitudeLongitudeValues=latLonValues;
 meta latitudes latitudes(values,0);

src/CMakeLists.txt

@@ -346,6 +346,7 @@ list( APPEND grib_api_srcs
     grib_nearest_class_latlon_reduced.c
     grib_nearest_class_sh.c
     grib_nearest_class_lambert_conformal.c
+    grib_nearest_class_mercator.c
     grib_nearest_class_polar_stereographic.c
     grib_iterator_class_polar_stereographic.c
     grib_iterator_class_lambert_azimuthal_equal_area.c

src/Makefile.am

@@ -361,6 +361,7 @@ libeccodes_la_prototypes= \
 	grib_nearest_class_latlon_reduced.c \
 	grib_nearest_class_sh.c \
 	grib_nearest_class_lambert_conformal.c \
+   	grib_nearest_class_mercator.c \
 	grib_nearest_class_polar_stereographic.c \
 	grib_iterator_class_polar_stereographic.c \
 	grib_iterator_class_lambert_azimuthal_equal_area.c  \

src/grib_nearest.c

@@ -323,6 +323,11 @@ int grib_nearest_find_generic(
         return ret;
     nearest->values_count = nvalues;
 
+    if (grib_is_earth_oblate(h)) {
+        grib_context_log(h->context, GRIB_LOG_ERROR, "Nearest neighbour functionality only supported for spherical earth.");
+        return GRIB_NOT_IMPLEMENTED;
+    }
+
     if ((ret = grib_get_long_internal(h, radius_keyname, &iradius)) != GRIB_SUCCESS)
         return ret;
     if (grib_is_missing(h, radius_keyname, &ret)) {

src/grib_nearest_class.h

@@ -2,6 +2,7 @@
 extern grib_nearest_class* grib_nearest_class_gen;
 extern grib_nearest_class* grib_nearest_class_lambert_conformal;
 extern grib_nearest_class* grib_nearest_class_latlon_reduced;
+extern grib_nearest_class* grib_nearest_class_mercator;
 extern grib_nearest_class* grib_nearest_class_polar_stereographic;
 extern grib_nearest_class* grib_nearest_class_reduced;
 extern grib_nearest_class* grib_nearest_class_regular;

src/grib_nearest_class_lambert_conformal.c

@@ -107,9 +107,9 @@ static int find(grib_nearest* nearest, grib_handle* h,
 {
     grib_nearest_lambert_conformal* self = (grib_nearest_lambert_conformal*)nearest;
     return grib_nearest_find_generic(
-        nearest, h, inlat, inlon, flags,
+        nearest, h, inlat, inlon, flags,  /* inputs */
 
-        self->values_key,
+        self->values_key,  /* outputs to set the 'self' object */
         self->radius,
         &(self->lats),
         &(self->lats_count),
@@ -119,7 +119,7 @@ static int find(grib_nearest* nearest, grib_handle* h,
         self->Ni,
         self->Nj,
 
-        outlats, outlons,
+        outlats, outlons,  /* outputs of the find function */
         values, distances, indexes, len);
 }
 

src/grib_nearest_class_mercator.c

@@ -107,9 +107,9 @@ static int find(grib_nearest* nearest, grib_handle* h,
 {
     grib_nearest_mercator* self = (grib_nearest_mercator*)nearest;
     return grib_nearest_find_generic(
-        nearest, h, inlat, inlon, flags,
+        nearest, h, inlat, inlon, flags, /* inputs */
 
-        self->values_key,
+        self->values_key,  /* outputs to set the 'self' object */
         self->radius,
         &(self->lats),
         &(self->lats_count),
@@ -119,7 +119,7 @@ static int find(grib_nearest* nearest, grib_handle* h,
         self->Ni,
         self->Nj,
 
-        outlats, outlons,
+        outlats, outlons,  /* outputs of the find function */
         values, distances, indexes, len);
 }
 

src/grib_nearest_class_polar_stereographic.c

@@ -107,9 +107,9 @@ static int find(grib_nearest* nearest, grib_handle* h,
 {
     grib_nearest_polar_stereographic* self = (grib_nearest_polar_stereographic*)nearest;
     return grib_nearest_find_generic(
-        nearest, h, inlat, inlon, flags,
+        nearest, h, inlat, inlon, flags, /* inputs */
 
-        self->values_key,
+        self->values_key,   /* outputs to set the 'self' object */
         self->radius,
         &(self->lats),
         &(self->lats_count),
@@ -119,7 +119,7 @@ static int find(grib_nearest* nearest, grib_handle* h,
         self->Ni,
         self->Nj,
 
-        outlats, outlons,
+        outlats, outlons,  /* outputs of the find function */
         values, distances, indexes, len);
 }
 

src/grib_nearest_factory.h

@@ -2,6 +2,7 @@
 { "gen", &grib_nearest_class_gen, },
 { "lambert_conformal", &grib_nearest_class_lambert_conformal, },
 { "latlon_reduced", &grib_nearest_class_latlon_reduced, },
+{ "mercator", &grib_nearest_class_mercator, },
 { "polar_stereographic", &grib_nearest_class_polar_stereographic, },
 { "reduced", &grib_nearest_class_reduced, },
 { "regular", &grib_nearest_class_regular, },

tests/grib_mercator.sh

@@ -30,5 +30,9 @@ EOF
 
 ${tools_dir}/grib_filter $tempFilter $input
 
+# Nearest function
+${tools_dir}/grib_ls -l 19,-97,1 $input > $tempOut
+grep -q "Point chosen #1 index=618" $tempOut
+
 # Clean up
 rm -f $tempFilter $tempOut