TELEDETECTION RADAR : DE L'IMAGE D'INTENSITE INITIALE AU CHOIX DU MODE DE CALIBRATION DES COEFFICIENTS DE DIFFUSION β0, σ0, γ0.

The current period is characterized by an abundance of free access radar data, the use of which is encouraged and facilitated by space agencies, the latter providing free software for image processing and analysis to users. At the same time, several academic or institutional sites offer explanatory resources (courses, software tutorials) on general or targeted topics intended to facilitate the use of images in most fields of application. In this paper, we wish to address and detail a particular point ; that of the physical concept of the radar measurement, through the various software processing proposed during a sequence of georeferencing-calibration of the images. This sequence, which combines geometrical and radiometric aspects, is found for applications relating to the characterization of the various media present on the surface of the ground or to facilitate the analysis of temporal sequences. After presenting the general aspects related to the power measured at the sensor and the various factors influencing this measurement, we will focus on the user practice, by discussing the different choices of coefficients β0, σ0, γ0, offered during a calibration following a geo-referencing, as well as on the taking into account, or not, slope effects in geometric and radiometric corrections affecting the image. Particular attention is paid to the coefficient γ0 whose variations as a function of local incidence are considered very low in the case of dense forests. [ABSTRACT FROM AUTHOR]