Gamma LAT: Reference Manual

soil_moisture

NAME
soil_moisture - Soil moisture retrieval algorithm (using reference function).

SYNOPSIS
soil_moisture <pwr> <pwr_ref> <mv_ref> <mv_out> <width> [dB_flag] [start] [nlines] [param_a] [param_b]

<pwr>	backscatter intensity image (float)
<pwr_ref>	reference backscatter intensity image (float)
<mv_ref>	reference volumetric soil moisture (float)
<mv_out>	output volumetric soil moisture map (float)
<width>	number of samples/row
[dB_flag]	flag indicating if pwr values are in dB (default:0=linear scale, 1=dB values)
[start]	starting line (default = 1)
[nlines]	number of lines to process (default: 0=to end of file)
[param_a]	model parameter a (default = 8.56)
[param_b]	model parameter b (default = 1.56)

EXAMPLE
soil_moisture 13258_13387.pwr1 pow_ref mv_ref 13258_13387.mv1 2500 0 1 0 8.56 1.56

For the reference backscatter image pow_ref the soil was frozen and therefore it was possible to estimate the reference soil moisture mv_ref.

INSTALLATION
Source code soil_moisture.c in ./src. For compilation adjust and use Makefile: Executable version soil_moisture in ../bin

AVAILABILITY
Uses type definition file typedef_ISP.h.

DESCRIPTION
soil_moisture generates a soil moisture map based on:
- backscatter image
- reference backscatter image
- reference soil moisture map

The retrieval algorithm used is:

intercept = (pwr_ref[dB] - 8.56 mv_ref) / (1 - 1.56 mv_ref)

and

mv = (pwr[dB] - intercept) / (8.56 - 1.56 intercept)

The input backscatter intensities (pwr, pwr_ref) can be given in linear scale or using dB values.

The model parameters (8.56, 1.56) describing the relationship between the slope and intercept of the regression between soil moisture and bacskcattering [dB] may be modified (for other sensors, polarizations, soils, etc.)

Soil moisture (volumetric) values are given in absolute values (typical values look like 0.25 (and not %: 25%)

Reference for the derivation and description of the soil moisture retrieval algorithm:
Wegmuller et al. 1997 , Final report to ESTEC Contract 11740/95/NL/PB(SC)

The soil moisture retrieval algorithm was developed for the retrieval of soil moisture for bare or sparsly vegetated fields from multi-temporal ERS data.

OPTIONS
The model parameters may be modified.

SEE ALSO
typedef_ISP.h.

DIAGNOSTICS
All messages are generally self-explanatory.

NOTES
The program soil_moisture may.c may be used as a starting point to develop other retrieval algorithms based.