qaa.c File Reference

#include <stdlib.h>
#include <math.h>
#include <stdarg.h>
#include <assert.h>
#include "qaa.h"

Include dependency graph for qaa.c:

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Functions
int	qaa_is_initialized (void)
int	qaa_init (int i410, int i440, int i490, int i555, int i670)
int	qaa_set_param (int param,...)
int	qaa_v6 (int nbands, double *wavel, double *Rrs, double *aw, double *bbw, double *rrs, double *u, double *a, double *bb, unsigned char *flags)
int	qaaf_v6 (int nbands, float *wavel, float *Rrs, float *aw, float *bbw, float *rrs, float *u, float *a, float *bb, unsigned char *flags)
int	qaa_decomp (int nbands, double *wavel, double *rrs, double *a, double *aw, double *adg, double *aph, unsigned char *flags)
int	qaaf_decomp (int nbands, float *wavel, float *rrs, float *a, float *aw, float *adg, float *aph, unsigned char *flags)

Detailed Description

Quasi-Analytic Algorithm.

Author

Paul Martinolich

Naval Research Laboratory, Stennis Space Center, MS

This code implements version 6 of the QAA algorithm which was based on the original algorithm Lee, at al (2002) "Deriving inherent optical properties from water color: A multi-band quasi-analytical algorithm for optically deep water" Applied Optics, (41) 27, 5755-5772, 2002

The version 4 update was presented as Appendix A in the paper Lee, et al (2007) "Euphotic zone depth: Its derivation and implication to ocean-color remote sensing" Journal of Geophysical Research, Vol 112, C03009, doi:10,1029/2006JC003802.

The version 5 update is available at IOCCG web site: http://www.ioccg.org/groups/Software_OCA/QAA_v5.pdf

The version 6 update is available at IOCCG web site: http://www.ioccg.org/groups/Software_OCA/QAA_v6.pdf

Additional routines are used to initialize indices and other parameters with the goal to make the code generic for use in SeaWiFS/MODIS processing as well as hyperspectral data from an ASD or PHILLS.

Likewise, the code duplicates routines for float or double type variables. The 'float' routines have an 'f' after the 'qaa' prefix.

The following code example shows a example of running the QAA algorithm on SeaWiFS data (with notes on how to run it for other sensor and using the 670nm path or chl path).

#include "qaa.h"
#define NBANDS 7
// inputs
int   idx410  = 0;
int   idx440  = 1;
int   idx490  = 2;
int   idx555  = 3;
int   idx670  = 4;
 
// SeaWiFS wavelengths (nm)
double wl[NBANDS] = { 412, 443, 490, 555, 670 };
 
// SeaWiFS band-averaged pure water absorption
double aw[NBANDS] = { 0.004641, 0.007095, 0.0015267, 0.032599, 0.4456 };
 
// SeaWiFS band-averaged pure water backscattering coefficient
double bbw[NBANDS] = { 0.003272, 0.002421, 0.001568, 0.0009394, 0.0004261 };
 
double Rrs[NBANDS];
 
// temporary space
 
double u[NBANDS], buf[4*NBANDS];
 
// outputs
 
double rrs[NBANDS];
double a[NBANDS], bb[NBANDS], adg[NBANDS], aph[NBANDS];
 
// read input Rrs
 
qaa_init( idx410, idx440, idx490, idx555, idx670);
 
// set the S parameter (default is 0.015)
qaa_set_param( QAA_S_PARAM, 0.011 );
 
// set the aw coefficients which differ based on sensor (Step 2)
// qaa_set_param( QAA_COEFS_PARAM, -1.204, -1.229, -0.395 ); // MODIS
// qaa_set_param( QAA_COEFS_PARAM, -1.273, -1.163, -0.295 ); // MERIS
// qaa_set_param( QAA_COEFS_PARAM, -1.146, -1.366, -0.469 ); // OCM1
// qaa_set_param( QAA_COEFS_PARAM, -1.318, -1.192, -0.206 ); // OCM2
// NOTE: OCM2 has no 670 band, but 620 can be used.
// qaa_set_param( QAA_COEFS_PARAM, -1.273, -1.366, -0.469 ); // SeaWiFS (default)
 
// run QAA using chl reference and decompose a into adg and aph components
// NOTE: if quality flags are undesired, a NULL can be passed to ignore them.
qaa_v6( NBANDS, wl, Rrs, rrs, u, buf, a, bb, NULL, NULL, flags );
qaa_decomp( NBANDS, wl, rrs, a, adg, aph, flags );
 
// write out results

Definition in file qaa.c.

Function Documentation

qaa_decomp()

int qaa_decomp	(	int	nbands,
		double *	wavel,
		double *	rrs,
		double *	a,
		double *	aw,
		double *	adg,
		double *	aph,
		unsigned char *	flags
	)

Quasi-Analytical Algorithm - decomposition of total absorption.

Parameters

[in]	nbands	number of bands in spectrum
[in]	wavel	wavelength of spectrum (nbands)
[in]	rrs	below-water remote sensing reflectance (nbands)
[in]	a	total absorption (nbands)
[in]	aw	pure-water absorption (nbands)
[out]	adg	gelbstuff absorption (nbands)
[out]	aph	phytoplankton absorption (nbands)
[out]	flags	quality flags (will be modified) or NULL

This implements Table 3 of the Quasi-Analytical Algorithm. It decomposes the total absorption into phytoplankton absorption and gelbstuff absorption.

This implementation adds a consistency check based on the phytoplankton absorption at 443nm to improve the decomposition of total absorption.

Definition at line 380 of file qaa.c.

qaa_init()

int qaa_init	(	int	i410,
		int	i440,
		int	i490,
		int	i555,
		int	i670
	)

initalize Quasi-Analytical Algorithm v4

Parameters

[in]	i410	0-relative index in spectrum of 410 nm
[in]	i440	0-relative index in spectrum of 440 nm
[in]	i490	0-relative index in spectrum of 490 nm
[in]	i555	0-relative index in spectrum of 555 nm
[in]	i670	0-relative index in spectrum of 670 nm

This routine should be called to initialize various parameters that may be adjusted in the QAA algorithm or that must be known apriori. For example, the user must supply the indices for various required band numbers and whether to perform the iteration in the QAA-555 algorithm (normally yes).

Definition at line 132 of file qaa.c.

qaa_is_initialized()

int qaa_is_initialized

(

void

)

determine if qaa algorithm properly initialized

Returns

1 if qaa_init has been previously called; 0, otherwise

Definition at line 113 of file qaa.c.

qaa_set_param()

int qaa_set_param	(	int	param,
			...
	)

set a parameter for Quasi-Analytical Algorithm

Parameters

[in]

param

name of parameter

This routine should be called to initialize various parameters that may be adjusted in the QAA algorithm or that must be known apriori. For example, the user must supply the indices for various required band numbers. Optionally, the user may define there own values for some parameters, like S.

Presently the only parameter the user may set is the S value.

Definition at line 163 of file qaa.c.

qaa_v6()

int qaa_v6	(	int	nbands,
		double *	wavel,
		double *	Rrs,
		double *	aw,
		double *	bbw,
		double *	rrs,
		double *	u,
		double *	a,
		double *	bb,
		unsigned char *	flags
	)

Quasi-Analytical Algorithm v6.

Parameters

[in]	nbands	number of bands in spectrum
[in]	wavel	wavelength of spectrum (nbands)
[in]	Rrs	above-water remote sensing reflectance (nbands)
[in]	aw	pure-water absorption (nbands)
[in]	bbw	pure-water back scattering (nbands)
[out]	rrs	below-water remote sensing reflectance (nbands)
[out]	u	ratio (nbands)
[out]	a	total absorption (nbands)
[out]	bb	backscattering (nbands)
[out]	flags	quality flags (will be modified) or NULL

This implements version 6 of the Quasi-Analytical Algorithm.

Definition at line 200 of file qaa.c.

qaaf_decomp()

int qaaf_decomp	(	int	nbands,
		float *	wavel,
		float *	rrs,
		float *	a,
		float *	aw,
		float *	adg,
		float *	aph,
		unsigned char *	flags
	)

Quasi-Analytical Algorithm - decomposition of total absorption.

See also

qaa_decomp()

Definition at line 450 of file qaa.c.

qaaf_v6()

int qaaf_v6	(	int	nbands,
		float *	wavel,
		float *	Rrs,
		float *	aw,
		float *	bbw,
		float *	rrs,
		float *	u,
		float *	a,
		float *	bb,
		unsigned char *	flags
	)

Quasi-Analytical Algorithm v4.

See also

qaa_v6()

Definition at line 279 of file qaa.c.