- LsM is sampled from bareland pixels in the image which are very bright and expected to be void of vegetation, like sandy beach
- Spectral LsM is intended to sit as the intersection of the Brightest Pixels Line and the Soil Line.
- this choice is not very sensitive
- LsM is adjusted so as to obtain a satisfactory fit of depths computed for BPL pixels in the calibration diagram: see big star on tarawa-subset_calibration
- CoefLM : this spectral LsM value may be altered using the CoefLM parameter in the -B argument
- a value higher or lower than 1.0 is used to slide spectral LsM up or down the observed Soil Line
- this does not affect the computed depth, while it widens or narrows the range of computed bottom reflectances (one more priviledge of a ratio method)