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Terrestrial laser scanning–New perspectives in 3D surveying
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Short Description: C Fröhlich, M Mettenleiter - … Archives of Photogrammetry, Remote Sensing and …, 2006 - isprs.org Having the environment in 3D as a CAD model (“digital factory The market of laser
scanners for terrestrial applications has developed ove
Content Inside: TERRESTRIAL LASER SCANNING NEW PERSPECTIVES IN 3D SURVEYING
Fröhlich, C.; Mettenleiter, M. Zoller + Fröhlich (Z+F) GmbH, Simoniusstr. 22, D-88239 Wangen, Germany Phone: +49-7522-9308-0 Fax: +49-7522-9308-52 email: info@zf-laser.com http: www.zf-laser.com KEY WORDS: Close Range Photogrammetry and 3D Scanning, Laser scanning, Terrestrial, Three-dimensional, investigating of laser scanners, applications, high precision scanning ABSTRACT Laser scanners are used more and more as surveying instruments for various applications. With the advance of high precision systems, capable of working in most real world environments under a variety of conditions, numerous applications have opened up. In the field of surveying laser scanners open up a new dimension with data capturing. Different industrial sectors require precise data of the environment in order to be able to have a as-build documentation of the facility. Especially as build documentation of plants (automotive, chemical, pharmaceutical etc.) has become a very sensitive and important new segment, as companies need to document their facilities. This is a basic requirement to plan and evaluate emergency situations (evacuation scenarios etc.) but also for simulation purposes of specific manufacturing cycles (car assembly etc.) as well as design studies. Having the environment in 3D as a CAD model ("digital factory") open up design studies without changing anything in the real environment and therefore causing no down time of production lines. This paper reports about several systems and physical technologies used for measuring distances and presents several products available in this area. Furthermore it presents technical specifications of different systems and summarises with a comparison of achievable results.
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INTRODUCTION
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Classification of terrestrial laser scanners
The market of laser scanners for terrestrial applications has developed over the last years quite successfully and the laser scanners are seen as surveying instruments which meet the requirements of industrial applications. At the moment several companies are offering products to the market. A direct comparison of these systems is difficult because of their technical specification and their physical measurement principle being different. Most systems are a combination of a one dimensional measurement system with a mechanical deflection system, directing the laser beam into different directions and measuring for each direction the distance to the closest object. The recent developments of terrestrial laser scanners open a wide variety of applications and therefore the adaptation of laser scanners is increasing. In contrast to traditional geodetic instruments (e.g. total stations, GPS), most of the available laser scanners are not well specified regarding accuracy, resolution and performance as well only a few systems are checked by independent institutes regarding their performance and to confirm manufacturer specifications. A comprehensive investigation procedure has not been developed yet, so individual tests show results of the available systems. The paper introduces technologies available with laser scanners. It reports the design of a laser scanner, consisting of a range measurement system and a deflection mirror and shows results of tests performed with the systems. It presents software for modelling purposes and compares three packages available by scanner manufacturers. It concludes with a summary of available systems and their performance data and gives an outlook to future developments needed for terrestrial developments.
A classification of terrestrial laser scanners is difficult to be done. There are several possibilities to do this, either based on the measurement principle (i.e. triangulation, phase or pulse) or based on the technical specifications achieved. First of all, there is no one universal laser scanner for all conceivable applications. Some scanners are suitable for indoor use and medium ranges (up to 100 m), other scanners are better for outdoor use with long ranges (up to some 100 m) and there are also scanners for close range applications (up to some meters) with a high precision. Dependent on the application the suited laser scanner has to be selected. Terrestrial laser scanners can be categorised by the principle of the distance measurement system. The distance measurement system correlates to both the range and the resulting accuracy of the system. Three different technologies for range measurements are used with laser scanners:
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Today, the most popular measurement system for laser scanners is the time of flight principle. This technique allows unambiguous measurements of distances up to several hundred of metres. The advantage of long ranges implies reasonable accuracy. Beside the time of flight principle, the phase measurement principle represents the other common technique for medium ranges. The range is restricted to one hundred metres. Accuracy of the measured distances within some millimetres are possible. For the sake of completeness, several close range laser scanners with ranges up to few meters are available. But, they are more for the use in industrial applications and reverse engineering (online monitoring in construction pro-
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