Empirical or semi-empirical methods

For the determination of bio-geophysical parameters many studies are based on statistical approaches that allow the definition of empirical or semi-empirical methods, so split according to how their definition/parametrisation depend on the dataset used in the calibration phase, or may usable to other similar data. In both cases, the approach is based on the development of statistical relationships between the spectral values measured by the sensor and the bio-geophysical parameters of the surface. The statistical analysis between radiometr ic data and bio-geophysical parameters used to build the model can make use of univariate or multivariate analysis techniques, including transformations of variables (eg, logarithms) and refer to both single bands or band combination  (eg vegetation index), etc. Depending on the objective of the work and the availability of ancillary data, satellite data to be used by the empirical/semi-empirical methods may be correct or not for the atmospheric effect.