Calibration of a Terrestrial Laser Scanner - Institute of Geodesy and ...

7.2 Outlook 133accuracy of single points, 3D accuracy of objects, e.g. spheres, would help users to distinguish betweenavailable laser scannersystems. Since laser scanning also means the processing of point clouds, the datatransfer and exchange between laser scanners and software packages is essential and should be simplified.Furthermore, the processing of point clouds has to be supported by fully-automatic algorithmsthe time for post-processing work. The limiting time factor is not only the data acquisition,processing of the huge numbers of point clouds.In the past three years another promising technique has been developed and mayto reducebut also therevolutionise the worldof 3D data capturing methods. It is called range-imaging (RIM) and is based on CMOS1 imagecalled range-imaging cameras acquire, with each single pixel of the CMOS chip, slopeobjectsand the camera. Thesensors. Sodistances betweencamera-like operation mode allows for directly deriving 3D coordinates byspatial resection using the camera characteristics, i.e. focal length and pixel coordinates, and the measuredslope distance. The intensity or amplitude of the demodulated signal complementthe 3D coordinates witha fourth dimension analogous to laser scanning. The data acquisition rate is extremely high,rates up to 50 frames per second, the range is limited to several meters, i.e.with frameclose-range applications, andthe accuracy is within the centimeter-scale [Kahlmann and Ingensand, 2005]. An example of one rangeimagingcamera is shown in Figure 7.2, the SwissRanger SR-2 by CSEM (Switzerland). The lens is locatedin the middle for acquiring the data, the visible array of LEDs is used as the emitting system for the distancemeasurement. The CCD/CMOS sensor is behind the lens. RIM cameras are small in dimensions, i.e. cen¬timeters, light in mass, i.e. some hundreds of a kilogram, and low in cost, i.e. below 1000 CHE Thus, theyare well-adapted for several applications, e.g. automotive, safety, security and surveillance, telemonitoring,robot vision, autonomous vehicles, and surveying.Figure 7.2: SwissRangerSR-2 by CSEM.CMOS: complementary metal-oxide-semiconductor