| PSSRa Algorithm Specification | |
The Pigment Specific Simple Ratio (chlorophyll index)
algorithm was developed by Blackburn (1998). It investigates the potential of a range of spectral approaches for quantifying pigments at the scale of the whole plant canopy
When applying existing narrow-band pigment indices, the PSSR algorithms have the strongest and most linear relationships with canopy concentration
per unit area of Chl a (Chlorophyll a), Chl b (Chlorophyll b) and Cars (carotenoids).
The PSSRa results from the following equation:
PSSRa = (IR_factor * near_IR) / (red_factor * red)
For Sentinel-2 the formula is:
B7 / B4, where (Central wavelength/Bandwidth): B7 = 783 nm (15 nm) and B4 = 665 nm (30 nm)
Also the processor computes an additional flags band called 'pssra_flags' with the following bit coding:
| Bit Position | Description |
|---|---|
| Bit 0 | The computed value for PSSRa is NAN or is Infinite |
| Bit 1 | The computed value for PSSRa is less than -1 (minus one) |
| Bit 2 | The computed value for PSSRa is greater than 1 (one) |