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/*
* (C) Copyright 2005- 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 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 numObs = 0;
size_t len = 0;
int i, err = 0;
int cnt = 0;
const char* infile = "../../data/bufr/asca_139.bufr";
char key_name[128];
in = fopen(infile, "rb");
if (!in) {
fprintf(stderr, "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) {
fprintf(stderr, "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);
/* Get latitude */
snprintf(key_name, sizeof(key_name), "latitude");
/* Check the size (including all the subsets) */
CODES_CHECK(codes_get_size(h, key_name, &len), 0);
if (len != numObs) {
fprintf(stderr, "Error: inconsistent number of %s values found!\n", key_name);
return 1;
}
/* Allocate memory for the values to be read. Each
* parameter must have the same number of values. */
lat = (double*)malloc(numObs * sizeof(double));
/* Get the values (from all the subsets) */
CODES_CHECK(codes_get_double_array(h, key_name, lat, &len), 0);
/* Get longitude */
snprintf(key_name, sizeof(key_name), "longitude");
/* Check the size (including all the subsets) */
CODES_CHECK(codes_get_size(h, key_name, &len), 0);
if (len != numObs) {
fprintf(stderr, "Error: inconsistent number of %s values found!\n", key_name);
return 1;
}
/* Get the values (from all the subsets) */
lon = (double*)malloc(numObs * sizeof(double));
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. */
snprintf(key_name, sizeof(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) {
fprintf(stderr, "Error: inconsistent number of %s values found!\n", key_name);
return 1;
}
/* Get the values (from all the subsets) */
bscatter = (double*)malloc(numObs * sizeof(double));
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;
}
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