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Airborne Laser Altimetry (ALA) has experienced a rapid increase in popularity as a method serving a wide range of applications in Remote Sensing, Geodesy, Geophysics and Geodynamics. Besides the ‘traditional’ approach of using laser scanning solely as a supplement for photogrammetry in acquiring digital terrain models, ALA has also been applied to various geoscience research problems. After a short overview of airborne laser altimetry activities in Europe, an application of airborne laser scanning dedicated to Alpine Glaciology is presented.

This tutorial paper gives an introduction and overview of various topics related to airborne laser scanning (ALS) as used to measure range to and reflectance of objects on the earth surface. After a short introduction, the basic principles of laser, the two main classes, i.e., pulse and continuous-wave lasers, and relations with respect to time-of-flight, range, resolution, and precision are presented. The main laser components and the role of the laser wavelength, including eye safety considerations, are explained. Different scanning mechanisms and the integration of laser with GPS and INS for position and orientation determination are presented. The data processing chain for producing digital terrain and surface models is outlined. Finally, a short overview of applications is given.

This chapter discusses the applied ranging principles and the achievable ranging accuracy is estimated by link budget calculations. It presents the Light Detection and Ranging (LiDAR) link budget calculation that was reduced to the simpler forms in order to highlight the key parameters that govern instrument performance. For understanding the functioning of the different LiDARs, for evaluating the performance of the instrument components and for selecting the right components appropriate for specific surveying tasks, the principles of LiDAR systems are described by subdividing the whole system into functional subunits. Most LiDARs are realized with conventional optics. Data handling for fullwave recording LiDARs is even more demanding, because the full receive pulse shape is digitized rather than simply ranging to its leading edge. The combination of LiDAR and Position and orientation system (POS) units may vary from survey to survey, and for research purposes often several POS are flown together for comparative studies.

The fusion of panoramic camera data with laser scanner data is a new approach and allows the combination of high-resolution image and depth data. Application areas are city modelling, virtual reality and documentation of the cultural heritage. Panoramic recording of image data is realized by a CCD-line, which is precisely rotated around the projection centre. In the case of other possible movements, the actual position of the projection centre and the view direction has to be measured. Linear moving panoramas e.g. along a wall are an interesting extension of such rotational panoramas. Here, the instantaneous position and orientation determination can be realized with an integrated navigation system comprising differential GPS and an inertial measurement unit. This paper investigates the combination of a panoramic camera and a laser scanner with a navigation system for indoor and outdoor applications. First it will be reported about laboratory experiments, which were carried out to obtain valid parameters about the surveying accuracy achievable with both sensors panoramic camera and laser scanner respectively. Then out door surveying results using a position and orientation system as navigation sensor will be presented and discussed.

The Institute of Navigation/University Stuttgart has developed an airborne Scanning Laser Altitude and Reflectance Sensor. This paper describes an approach to automatically detect and extract artificial surface objects using the data of imaging laser altimeters. Laser altimeters register surface topography directly in three spatial dimensions by measuring the distance to individual surface points. Beyond mere ranging advanced imaging laser altimeters like the Scanning Laser Altitude and Reflectance Sensor (ScaLARS) are also able to actively measure surface reflectance. By fusing both the 3-D geometry and surface reflectance, object detection and identification can be done automatically. In a first step, surface objects are detected by applying a morphology-based filter to the elevation data. In order to detect also large buildings which tend to make morphological filtering fail an additional approach based on a progressive local histogram analysis of elevation is used. The detected surface objects are then separated into artificial objects (buildings) and natural objects (vegetation) in the second step, using surface reflectance data, and/or elevation 'texture' and surface orientation. To demonstrate the effectiveness of these identification criteria, they are applied to a test data set collected with the ScaLARS laser altimeter.

This paper presents a 3D-Imaging Laser Scanner (3D-ILS) for close range survey for up to 10 meters. The 3D-ISL is eyesafe and works with a visible semiconductor laser diode transmitting at 670 nm. The large ranging dynamic is achieved by measuring the phase difference between the transmitted and received intensity modulated signal. Due to the high modulation frequency of 314 MHz measurement accuracies about 0.1 mm are possible with high measurement rates. Besides the slant range, the system detects laser light backscattered from the object surface under survey. This means that three dimensional images are obtained, if the scanner moves the laserbeam line by line across the object's surface. After explaining the functioning of the 3D-ILS and calculating the theoretical slant ranging performance, typical application examples will be presented which verify the theoretical results and demonstrate the wide application field for the laser scanner which is e.g. CAD, CAM, rapid prototyping, close range-, industrial- and architectural-survey. An application highlight is the survey of a reconstructed skeleton of a dinosaur.

At the Institute of Navigation a new method of surveying historical sites and monuments has been developed and applied in field experiments. This method uses a 4D LaserScanner and sophisticated software to measure the 3D structure of the observed object and to partition and abstract the object's surface for automatic plan-drawing generation. By showing typical measurements and evaluation results, the application possibilities of the new method for conservation and restoration of historical buildings is demonstrated.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Today non contacting optical 3D-digitizers feature high sampling rates and are capable of obtaining highly resolved 3D images of object surfaces. In general thesedigital range images contain a large amount of data and require powerful computersand large memories for further processing. It will be shown that the number of datacan be reduced by eliminating the redundant information contained in digital rangeimages by applying pattern recognition techniques. Surface generation, contour linesgeneration, triangulation and volume generation, will be explained for the differentoperation levels with respect to CAD/CAM. 1. Introduction Today 3D-Digitizers with an optical sensor feature high sampling rates and the abilityof digitizing complex objects and object surlaces in practical times. Due to the highsampling rate, the 3D measurement points are located so close to each other on theobject's surface that a highly resolved image is obtained. However, these digitalrange images contain a large amount of data with no relevance for volume oriented

An experimental setup of a semiconductor laser scanner for 3D-mapping is described. First measurement results are presented. The experimental results are discussed and estimations for a future remote sensing system are given. Finally the main possibilities for applications of a semiconductor laser mapper are identified.