Automatic Merging of Lidar Point-Clouds Using Data from Low-Cost GPS/IMU Systems

Stationary lidar (Light Detection and Ranging) systems are often used to collect 3-D data (point clouds) that can be used for terrain modelling. The lidar gathers scans which are then merged together to map a terrain. Typically this is done using a variant of the well-known Iterated Closest Point (ICP) algorithm when position and pose of the lidar scanner is not accurately known. One difficulty with the ICP algorithms is that they can give poor results when points that are not common to both scans (outliers) are matched together. With the advent of MEMS (microelectromechanical systems)-based GPS/IMU systems, it is possible to gather coarse position and pose information at a low cost. This information is not accurate enough to merge point clouds directly, but can be used to assist the ICP algorithm during the merging process. This paper presents a method called Sphere Outlier Removal (SOR), which accurately identifies outliers and inliers, a necessary prerequisite to using the ICP algorithm. SOR incorporates the information from a low cost GPS/IMU to perform this identification. Examples are presented which illustrate the improvement in the accuracy of merged point clouds when the SOR algorithm is used

Premiers resultats cliniques de l'utilisation d'un lithotriteur laser a colorant pulse Rhodamine 590 dans le traitement des calculs de l'uretere. [First clinical results using a pulsed dye laser Rhodamine 590 lithotripter in treatment of ureteral calculi]

A collaborative study about a pulsed dye laser Rhodamin 590 was undergone, 2 years ago, between the laser application center of EPFL and both urological departments of the university of Geneva and the university of Lausanne. First clinical results are presented. Ten patients have been treated for various ureteral stones, mainly calcium oxalate stones. Laser fragmentation was successful in seven cases. No serious complication was noted. Fragmentation efficiency seems better with a 320 microns fiber than with a 200 microns fiber