mirror of
https://github.com/Unidata/netcdf-c.git
synced 2024-12-21 08:39:46 +08:00
162 lines
4.4 KiB
C
162 lines
4.4 KiB
C
/*! \file
|
|
Example program for reading a 4D netCDF file
|
|
|
|
\ingroup tutorial
|
|
|
|
This is an example which reads some 4D pressure and temperatures. The
|
|
data file read by this program is produced by the companion program
|
|
pres_temp_4D_wr.c. It is intended to illustrate the use of the netCDF
|
|
C API.
|
|
|
|
This is part of the netCDF package. Copyright 2006-2011 University
|
|
Corporation for Atmospheric Research/Unidata. See COPYRIGHT file for
|
|
conditions of use. Full documentation of the netCDF can be found at
|
|
http://www.unidata.ucar.edu/software/netcdf/docs.
|
|
|
|
*/
|
|
|
|
#include <stdio.h>
|
|
#include <string.h>
|
|
#include <netcdf.h>
|
|
|
|
/* This is the name of the data file we will read. */
|
|
#define FILE_NAME "pres_temp_4D.nc"
|
|
|
|
/* We are reading 4D data, a 2 x 6 x 12 lvl-lat-lon grid, with 2
|
|
timesteps of data. */
|
|
#define NDIMS 4
|
|
#define NLAT 6
|
|
#define NLON 12
|
|
#define LAT_NAME "latitude"
|
|
#define LON_NAME "longitude"
|
|
#define NREC 2
|
|
#define REC_NAME "time"
|
|
#define LVL_NAME "level"
|
|
#define NLVL 2
|
|
|
|
/* Names of things. */
|
|
#define PRES_NAME "pressure"
|
|
#define TEMP_NAME "temperature"
|
|
#define UNITS "units"
|
|
#define DEGREES_EAST "degrees_east"
|
|
#define DEGREES_NORTH "degrees_north"
|
|
|
|
/* These are used to calculate the values we expect to find. */
|
|
#define SAMPLE_PRESSURE 900
|
|
#define SAMPLE_TEMP 9.0
|
|
#define START_LAT 25.0
|
|
#define START_LON -125.0
|
|
|
|
/* For the units attributes. */
|
|
#define UNITS "units"
|
|
#define PRES_UNITS "hPa"
|
|
#define TEMP_UNITS "celsius"
|
|
#define LAT_UNITS "degrees_north"
|
|
#define LON_UNITS "degrees_east"
|
|
#define MAX_ATT_LEN 80
|
|
|
|
/* Handle errors by printing an error message and exiting with a
|
|
* non-zero status. */
|
|
#define ERR(e) {printf("Error: %s\n", nc_strerror(e)); return 2;}
|
|
|
|
int
|
|
main()
|
|
{
|
|
int ncid, pres_varid, temp_varid;
|
|
int lat_varid, lon_varid;
|
|
|
|
/* The start and count arrays will tell the netCDF library where to
|
|
read our data. */
|
|
size_t start[NDIMS], count[NDIMS];
|
|
|
|
/* Program variables to hold the data we will read. We will only
|
|
need enough space to hold one timestep of data; one record. */
|
|
float pres_in[NLVL][NLAT][NLON];
|
|
float temp_in[NLVL][NLAT][NLON];
|
|
|
|
/* These program variables hold the latitudes and longitudes. */
|
|
float lats[NLAT], lons[NLON];
|
|
|
|
/* Loop indexes. */
|
|
int lvl, lat, lon, rec, i = 0;
|
|
|
|
/* Error handling. */
|
|
int retval;
|
|
|
|
/* Open the file. */
|
|
if ((retval = nc_open(FILE_NAME, NC_NOWRITE, &ncid)))
|
|
ERR(retval);
|
|
|
|
/* Get the varids of the latitude and longitude coordinate
|
|
* variables. */
|
|
if ((retval = nc_inq_varid(ncid, LAT_NAME, &lat_varid)))
|
|
ERR(retval);
|
|
if ((retval = nc_inq_varid(ncid, LON_NAME, &lon_varid)))
|
|
ERR(retval);
|
|
|
|
/* Read the coordinate variable data. */
|
|
if ((retval = nc_get_var_float(ncid, lat_varid, &lats[0])))
|
|
ERR(retval);
|
|
if ((retval = nc_get_var_float(ncid, lon_varid, &lons[0])))
|
|
ERR(retval);
|
|
|
|
/* Check the coordinate variable data. */
|
|
for (lat = 0; lat < NLAT; lat++)
|
|
if (lats[lat] != START_LAT + 5.*lat)
|
|
return 2;
|
|
for (lon = 0; lon < NLON; lon++)
|
|
if (lons[lon] != START_LON + 5.*lon)
|
|
return 2;
|
|
|
|
/* Get the varids of the pressure and temperature netCDF
|
|
* variables. */
|
|
if ((retval = nc_inq_varid(ncid, PRES_NAME, &pres_varid)))
|
|
ERR(retval);
|
|
if ((retval = nc_inq_varid(ncid, TEMP_NAME, &temp_varid)))
|
|
ERR(retval);
|
|
|
|
/* Read the data. Since we know the contents of the file we know
|
|
* that the data arrays in this program are the correct size to
|
|
* hold one timestep. */
|
|
count[0] = 1;
|
|
count[1] = NLVL;
|
|
count[2] = NLAT;
|
|
count[3] = NLON;
|
|
start[1] = 0;
|
|
start[2] = 0;
|
|
start[3] = 0;
|
|
|
|
/* Read and check one record at a time. */
|
|
for (rec = 0; rec < NREC; rec++)
|
|
{
|
|
start[0] = rec;
|
|
if ((retval = nc_get_vara_float(ncid, pres_varid, start,
|
|
count, &pres_in[0][0][0])))
|
|
ERR(retval);
|
|
if ((retval = nc_get_vara_float(ncid, temp_varid, start,
|
|
count, &temp_in[0][0][0])))
|
|
ERR(retval);
|
|
|
|
/* Check the data. */
|
|
i = 0;
|
|
for (lvl = 0; lvl < NLVL; lvl++)
|
|
for (lat = 0; lat < NLAT; lat++)
|
|
for (lon = 0; lon < NLON; lon++)
|
|
{
|
|
if (pres_in[lvl][lat][lon] != SAMPLE_PRESSURE + i)
|
|
return 2;
|
|
if (temp_in[lvl][lat][lon] != SAMPLE_TEMP + i)
|
|
return 2;
|
|
i++;
|
|
}
|
|
|
|
} /* next record */
|
|
|
|
/* Close the file. */
|
|
if ((retval = nc_close(ncid)))
|
|
ERR(retval);
|
|
|
|
printf("*** SUCCESS reading example file pres_temp_4D.nc!\n");
|
|
return 0;
|
|
}
|