nc_gridutils.c File Reference

#include "nc_gridutils.h"

Include dependency graph for nc_gridutils.c:

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Macros
#define	NEW_CACHE_SIZE   240000000
#define	NEW_CACHE_NELEMS   1001
#define	NEW_CACHE_PREEMPTION   .75

Functions
void	handle_nc_error (int status, char *file, int line)
var_info_t *	allocate_varinfo ()
var_info_t *	load_varinfo (int ncid, int varid)
int	find_varid (int ncid, const char *varnames[], int *varid)
grid_info_t *	allocate_gridinfo ()
int	init_gridinfo (char *filename, const char *varnames[], grid_info_t *grid)
int	fix_latlon (float *lat, float *lon)
int	latlon_findex (grid_info_t *grid, float lat, float lon, double *findex)
int	latlon_index (grid_info_t *grid, float lat, float lon, size_t *index)
int	get_bylatlon (grid_info_t *grid, float lat, float lon, double *value)
int	has_extra_column (grid_info_t *grid)
int	get_grid_area (grid_info_t *grid, float north, float south, float east, float west, grid_area_t *area)
int	interp_gridvar (grid_info_t *grid, float lat, float lon, double *result)
void	print_gridinfo (grid_info_t grid)

Detailed Description

Convenience utilities for handling NetCDF4 gridded variables.

Author

Gwyn Fireman

Ocean Ecology Laboratory, NASA Goddard Space Flight Center

Definition in file nc_gridutils.c.

Macro Definition Documentation

NEW_CACHE_NELEMS

#define NEW_CACHE_NELEMS   1001

Definition at line 10 of file nc_gridutils.c.

NEW_CACHE_PREEMPTION

#define NEW_CACHE_PREEMPTION   .75

Definition at line 11 of file nc_gridutils.c.

NEW_CACHE_SIZE

#define NEW_CACHE_SIZE   240000000

Definition at line 9 of file nc_gridutils.c.

Function Documentation

allocate_gridinfo()

grid_info_t* allocate_gridinfo

(

)

Allocate memory for structure describing grid.

Return values

grid	Empty structure for describing gridded variable.

Definition at line 107 of file nc_gridutils.c.

allocate_varinfo()

var_info_t* allocate_varinfo

(

)

Allocate memory for structure describing NetCDF variable.

Return values

var	Empty structure for describing NetCDF variable.

Definition at line 34 of file nc_gridutils.c.

find_varid()

int find_varid	(	int	ncid,
		const char *	varnames[],
		int *	varid
	)

Find ID of first variable found in input list.

Parameters

[in]	ncid	NetCDF ID, from a previous call to nc_open(),
[in]	varnames	Null-terminated list of possible variable names.
[out]	varid	NetCDF variable ID

Returns

Error if no variable found.

Definition at line 83 of file nc_gridutils.c.

fix_latlon()

int fix_latlon	(	float *	lat,
		float *	lon
	)

Force coordinates into range: {-90 <= lat < 90} and {-180 <= lon < 190}

Parameters

[in,out]

lat,lon

Desired geographic coordinates.

Returns

Error if either coordinate is NaN.

Definition at line 281 of file nc_gridutils.c.

get_bylatlon()

int get_bylatlon	(	grid_info_t *	grid,
		float	lat,
		float	lon,
		double *	value
	)

Read gridded variable value nearest to specified coordinates.

Parameters

[in]	grid	Structure describing grid.
[in]	lat,lon	Desired geographic coordinates.
[out]	value	Pointer to value, or FillValue if not found.

Returns

Error if coordinates outside of grid range. (0=good)

Definition at line 368 of file nc_gridutils.c.

get_grid_area()

int get_grid_area	(	grid_info_t *	grid,
		float	north,
		float	south,
		float	east,
		float	west,
		grid_area_t *	area
	)

Read gridded variable values covering specified boundaries.

Parameters

[in]	grid	Structure describing grid.
[in]	north,south,east,west	Geographic boundaries of desired area.
[out]	area	Structure contains and describes extracted area.

Returns

Error if any boundary set outside of grid range.

Definition at line 406 of file nc_gridutils.c.

handle_nc_error()

void handle_nc_error	(	int	status,
		char *	file,
		int	line
	)

Print NetCDF error message and exit.

Parameters

[in]	status	NetCDF error status.
[in]	file	Originating FILE.
[in]	line	Originating LINE.

Definition at line 21 of file nc_gridutils.c.

has_extra_column()

int has_extra_column

(

grid_info_t *

grid

)

Determine whether grid has extra longitude column. Needed when extracting area crossing +/- 180 degrees.

Parameters

[in]

grid

Structure describing grid.

Returns

TRUE: has extra longitude column.

FALSE: no extra longitude column.

Definition at line 394 of file nc_gridutils.c.

init_gridinfo()

int init_gridinfo	(	char *	filename,
		const char *	varnames[],
		grid_info_t *	grid
	)

Load information about gridded variable from a file.

Parameters

[in]	filename
[in]	varnames	Null-terminated list of possible variable names.
[out]	grid	Structure describing grid.

Returns

Error status.

Definition at line 132 of file nc_gridutils.c.

interp_gridvar()

int interp_gridvar	(	grid_info_t *	grid,
		float	lat,
		float	lon,
		double *	result
	)

Get bilinear interpolation of any gridded variable.

Parameters

[in]	grid	Structure describing grid.
[in]	lat,lon	Desired geographic coordinates.
[out]	result	Pointer to interpolated value, or FillValue if not found.

Returns

Error if coordinates outside of grid range.

Remarks

nc_get_var1_double will automatically convert native type to double - see http://www.unidata.ucar.edu/software/netcdf/docs/netcdf/Type-Conversion.html

Definition at line 529 of file nc_gridutils.c.

latlon_findex()

int latlon_findex	(	grid_info_t *	grid,
		float	lat,
		float	lon,
		double *	findex
	)

Find floating point index of specified coordinates within gridded variable.

Parameters

[in]	grid	Structure describing grid.
[in]	lat,lon	Desired geographic coordinates.
[out]	findex	Indices of [y,x] corresponding to [lat,lon].

Returns

Error if coordinates outside of grid range.

Definition at line 312 of file nc_gridutils.c.

latlon_index()

int latlon_index	(	grid_info_t *	grid,
		float	lat,
		float	lon,
		size_t *	index
	)

Find integer index of specified coordinates within gridded variable.

Parameters

[in]	grid	Structure describing grid.
[in]	lat,lon	Desired geographic coordinates.
[out]	index	Indices of [y,x] corresponding to [lat,lon].

Returns

Error if coordinates outside of grid range. (0=good)

Definition at line 342 of file nc_gridutils.c.

load_varinfo()

var_info_t* load_varinfo	(	int	ncid,
		int	varid
	)

Read NetCDF variable attributes and load into structure.

Parameters

[in]	ncid	NetCDF ID, from a previous call to nc_open(),
[in]	varid	NetCDF variable ID

Return values

var	Structure describing NetCDF variable.

Definition at line 52 of file nc_gridutils.c.

print_gridinfo()

void print_gridinfo

(

grid_info_t

grid

)

Print grid description structure.

Parameters

[in]

grid

Structure describing grid.

Definition at line 592 of file nc_gridutils.c.