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# nearest.c

nearest.c How to find the nearest grid points.

    00001
    00010 /*
    00011  * C Implementation: fieldset
    00012  *
    00013  * Description: how to use a fieldset.
    00014  *
    00015  *
    00016  * Author: Enrico Fucile
    00017  *
    00018  *
    00019  */
    00020
    00021 #include <stdio.h>
    00022 #include <stdlib.h>
    00023 #include <string.h>
    00024
    00025 #include "grib_api.h"
    00026
    00027 void usage(char* prog) {
    00028   printf("Usage: %s grib_file grib_file ...\n",prog);
    00029   exit(1);
    00030 }
    00031
    00032 int main(int argc, char** argv) {
    00033   int err = 0;
    00034   long step=0;
    00035   size_t nfiles;
    00036   int i=0;
    00037   grib_fieldset* set=NULL;
    00038   grib_handle* h=NULL;
    00039   char param[20]={0,};
    00040   size_t len=20;
    00041   double lats[4]={0,};
    00042   double lons[4]={0,};
    00043   double values[4]={0,};
    00044   double distances[4]={0,};
    00045   int indexes[4]={0,};
    00046   char* order_by="param,step";
    00047
    00048   size_t size=4;
    00049   double lat=-40,lon=15;
    00050   int mode=0;
    00051   int count;
    00052   char** filenames;
    00053   grib_nearest* nearest=NULL;
    00054
    00055   if (argc < 2) usage(argv[0]);
    00056
    00057   nfiles=argc-1;
    00058   filenames=(char**)malloc(sizeof(char*)*nfiles);
    00059   for (i=0;i<nfiles;i++)
    00060     filenames[i]=(char*)strdup(argv[i+1]);
    00061
    00062   set=grib_fieldset_new_from_files(0,filenames,nfiles,0,0,0,order_by,&err);
    00063   GRIB_CHECK(err,0);
    00064
    00065   printf("\nordering by %s\n",order_by);
    00066   printf("\n%d fields in the fieldset\n",grib_fieldset_count(set));
    00067   printf("n,step,param\n");
    00068
    00069   mode=GRIB_NEAREST_SAME_GRID |  GRIB_NEAREST_SAME_POINT;
    00070   count=1;
    00071   while ((h=grib_fieldset_next_handle(set,&err))!=NULL) {
    00072     GRIB_CHECK(grib_get_long(h,"step",&step),0);
    00073         len=20;
    00074     GRIB_CHECK(grib_get_string(h,"param",param,&len),0);
    00075
    00076     printf("%d %ld %s  ",count,step,param);
    00077     if (!nearest) nearest=grib_nearest_new(h,&err);
    00078     GRIB_CHECK(err,0);
    00079     GRIB_CHECK(grib_nearest_find(nearest,h,lat,lon,mode,lats,lons,values,distances,indexes,&size),0);
    00080     for (i=0;i<4;i++) printf("%d %.2f %.2f %g %g - ",
    00081          (int)indexes[i],lats[i],lons[i],distances[i],values[i]);
    00082     printf("\n");
    00083
    00084     grib_handle_delete(h);
    00085     count++;
    00086   }
    00087
    00088   if (nearest) grib_nearest_delete(nearest);
    00089
    00090   if (set) grib_fieldset_delete(set);
    00091
    00092   return 0;
    00093 }