Description
This example shows: how to read data for a given beam from scatterometer BUFR messages.Source code
bufr_read_scatterometer.c
/* * Copyright 2005-2015 ECMWF. * * This software is licensed under the terms of the Apache Licence Version 2.0 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. * * In applying this licence, ECMWF does not waive the privileges and immunities granted to it by * virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction. */ /* * C Implementation: bufr_read_scatterometer * * Description: how to read data for a given beam from scatterometer BUFR messages. * */ /* * Please note that scatterometer data can be encoded in various ways in BUFR. Therefore the code * below might not work directly for other types of SYNOP messages than the one used in the * example. It is advised to use bufr_dump to understand the structure of the messages. */ #include "eccodes.h" int main(int argc,char* argv[]) { FILE* in = NULL; /* Message handle. Required in all the eccodes calls acting on a message.*/ codes_handle* h=NULL; double *lat=NULL, *lon=NULL, *bscatter=NULL; long longVal; double doubleVal; size_t numObs,len; int i, err=0; int cnt=0; char* infile = "../../data/bufr/asca_139.bufr"; char key_name[128]; in=fopen(infile,"r"); if (!in) { printf("ERROR: unable to open file %s\n", infile); return 1; } /* Loop over the messages in the bufr file */ while ((h = codes_handle_new_from_file(NULL,in,PRODUCT_BUFR,&err)) != NULL || err != CODES_SUCCESS) { if (h == NULL) { printf("Error: unable to create handle for message %d\n",cnt); cnt++; continue; } printf("message: %d\n",cnt); /* We need to instruct ecCodes to expand the descriptors * i.e. unpack the data values */ CODES_CHECK(codes_set_long(h,"unpack",1),0); /* The BUFR file contains a single message with 2016 subsets in a compressed form. * It means each subset has exactly the same structure: they store one location with * several beams and one backscatter value in each beam. * * To print the backScatter values for beamIdentifier=2 from all the subsets * we will simply access the key by condition (see below) */ /* Get the total number of subsets. */ CODES_CHECK(codes_get_long(h,"numberOfSubsets",&numObs),0); printf("Number of values: %ld\n",numObs); /* Allocate memory for the values to be read. Each * parameter must have the same number of values. */ lat = malloc(numObs*sizeof(double)); lon = malloc(numObs*sizeof(double)); bscatter = malloc(numObs*sizeof(double)); /* Get latitude */ sprintf(key_name,"latitude"); /* Check the size (including all the subsets) */ CODES_CHECK(codes_get_size(h,key_name,&len),0); if(len != numObs) { printf("inconsistent number of %s values found!\n",key_name); return 1; } /* Get the values (from all the subsets) */ CODES_CHECK(codes_get_double_array(h,key_name,lat,&len),0); /* Get longitude */ sprintf(key_name,"longitude"); /* Check the size (including all the subsets) */ CODES_CHECK(codes_get_size(h,key_name,&len),0); if(len != numObs) { printf("inconsistent number of %s values found!\n",key_name); return 1; } /* Get the values (from all the subsets) */ CODES_CHECK(codes_get_double_array(h,key_name,lon,&len),0); /* Get backScatter for beam two. We use an access by condition for this key. */ sprintf(key_name,"/beamIdentifier=2/backscatter"); /* Check the size (including all the subsets) */ CODES_CHECK(codes_get_size(h,key_name,&len),0); if(len != numObs) { printf("inconsistent number of %s values found!\n",key_name); return 1; } /* Get the values (from all the subsets) */ CODES_CHECK(codes_get_double_array(h,key_name,bscatter,&len),0); /* Print the values */ printf("pixel lat lon backscatter \n"); printf("-------------------------------\n"); for(i=0; i < numObs; i++) { printf("%4d %.3f %.3f %.3f \n", i+1,lat[i],lon[i],bscatter[i]); } /* Delete handle */ codes_handle_delete(h); /* Release memory */ free(lat); free(lon); free(bscatter); cnt++; } fclose(in); return 0; }