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

4Static Laser ScanningThis chapter discusses the post-processing of 3D point clouds as applied to static laser scanning. Staticlaser scanning implies that the objectsto be scanned and the laser scanner do not move relative to eachother during the data acquisition process. Post-processing of 3D point clouds requires software packagesto derive the final products, e.g. 3D models. Since the implemented algorithms in these software packagesare not fully automated, the operator has to assist the software. Thus, the process of deriving the finalproduct based on the 3D point cloud is time-consuming. The time ratio between post-processingscanning point clouds and data acquisition can be upaspects of data processing, registration, and modelingto 10 : 1or more. The followingand visualization.of lasersections cover some4.1 Data ProcessingLaser scanning is one of the fastest data acquisition techniques in geodesy and generates a hugenumber ofpoints, which describe the environment, in a short time. However, data acquisition produces blunders andnoise within the point clouds. Noise can be distinguished in white noise and coloured noise. Here, noise isassumed to be white noise and Gaussian noise. The following sections givean overview of the conceivableerrors and error sources. They result in noisy data and have to be processed by applying special filteringand noise reduction techniques.4.1.1 Blunder DetectionThe laser scannersystem acquires data within a distance and an intensity interval. Sometimes, only datawithin a specific range regarding distance and intensity values are required. The pointswhich fulfil theserequirements can easily be separated from the points that do not fulfil the requirements by introducingminimum and maximum limits for both range and intensity data, a threshold:rangemm