Soil line estimation
When plotting the NIR reflectances of a multispectral image as a function of the Red reflectances, one obtains a scatterplot which is nearly completely above a straight line.
This line represents the positive correlation between the NIR and the Red for soil pixels.
The parameters of this line (slope and offset) are needed by several vegetation indices.
The goal here is to automatically estimate the parameters of the line from a multispectral image.
The easiest strategy is to built the scatterplot, keep the points which are minima for NIR and maxima for Red, and compute a linear regression.