Normalization Of Lidar Intensity Data Based On Range And Surface Incidence Angle

The analysis of airborne laser scanner data to extr act surface features is of great interest in photog rammetric research. Especially for applications based on airborne measurements, where the intensity is crucial (e.g. for segmentation, cl assification or visualization purposes), a normalization considering the beam div ergence, the incidence angle and the atmospheric at tenuation is required. Our investigations show that the same material of a sur face (e.g. gabled roof) yields to different measure d values for the intensity. These values are strongly correlated to the incidence ang le of the laser beam on the surface. Therefore the intensity value is improved with the incidence angle derived by the sensor and objec t position as well as its surface orientation. The surface orientation is estimated by the eigenvectors of the covariance matrix includ ing all object points inside a close environment. F urther the atmospheric attenuation is estimated. The adaptation of vegetat ion areas is disregarded in this study. After these improvements the intensity does no longer depend on the incidence angle but may be influenced by the material of the object surface on ly. For surface modelling the Phong model is introduced, considering diffuse and specular backscattering characteristics of the surf ace. A measurement campaign was carried out to investigate the influences of th e incidence angle on the measured intensity. By cons idering the incidence angle and the distance between sensor and object the laser da ta captured from different flight paths (data strip es) can be successfully fused. In our experiments it could be shown that the radiomet ric normalization of the intensity for the investig ated areas are improved.