Plant Water Retrieval (PWR)¶
About¶
The Plant Water Retrieval (PWR) tool uses is an efficient algorithm to directly extract quantitative water content information in [g cm-2] or [cm] from hyperspectral images. It applies the Beer-Lambert law [1] to inversely determine the optical thickness d of the water layer responsible for the water absorption feature at 970 nm using water absorption coefficients \({\alpha}\) for pure liquid water. \({\Phi}\) 0 denotes the incident radiation intensity and \({\Phi}\) is the attenuated radiation intensity.
[1] |
After calibration over various validation datasets (refer to Wocher et al. (2018) for detailed information) the final PWR equation [2] is as follows:
[2] |
with R 0 being the measured reflectance. The algorithm stops when the sum of the residuals to the assumed dry reflectance (Figure 1) is reached.
Getting Started¶
Select a GDAL readable hyperspectral input image via the … button and define a location for the output image ….
If you need to speed up the calculation a
NDVI threshold
for vegetation pixels can be assigned.Select an
Output No Data
value for the output image.If your input image is of integer type, assign a division factor to obtain relative reflectances expected by the algorithm.
Click Run to start the plant water retrieval algorithm.