Un modello geometrico per la calibrazione di dati laser terrestri

This paper deals with the calibration of terrestrial laser intensity measures. As known, 3D terrestrial laser scanner provide with a great amount of geometric data. An important and still seldom used information is the one given by laser backscattering. In this paper we propose a geometric algorithm for terrestrial laser intensity calibration, based onto two different steps. Firstly a distancebased calibration is computed, taking into account the fact that a laser beam varies its intensity when passing through a given medium. In this phase an global air absorbtion coefficient is estimated. Secondly, two separate geometric reflectance models are implemented, depending on the acquired features whose intensity measures need to be calibrated. Lambertian and Lommel-Seeliger reflectance models were implemented initially in MatLab® environment and secondly ported in IDL® language, both leading to a new DN (Digital Number), defined as pseudo-reflectance. Differently from a common data stretching procedure, results so far obtained with this method, show the possibility to appreciate micro-discontinuities in pseudo-reflectance data, usually corresponding to non homogeneous areas in the object acquired. This work has been developed in the frame of the research project INTERREG IIIA Italy-Slovenia, while the data acquisition campaign has been entirely carried on by the D.I.A.Pr.E.M. research laboratory group of the Architecture Department of the University of Ferrara.