Processing of laser scanner data—algorithms and applications

https://doi.org/10.1016/S0924-2716(99)00008-8Get rights and content

Abstract

Airborne laser scanning systems are opening new possibilities for surveys and documentation of difficult areas and objects, such as dense city areas, forest areas and electrical power lines. Laser scanner systems available on the market are presently in a fairly mature state of art while the processing of airborne laser scanner data still is in an early phase of development. To come from irregular 3D point clouds to useful representations and formats for an end-user requires continued research and development of methods and algorithms for interpretation and modelling. This paper presents some methods and algorithms concerning filtering for determining the ground surface, DEM, classification of buildings for 3D City Models and the detection of electrical power lines. The classification algorithms are based on the Minimum Description Length criterion. The use of reflectance data and multiple echoes from the laser scanner is examined and found to be useful in many applications.

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Background

Laser scanner systems available on the market are presently in a fairly mature state of art, where most of technical hardware difficulties and system integration problems have been solved. The systems are very complex, being more a `geodetic' system on the data acquisition part and more a `photogrammetric' system on the data processing part.

What very much remains is the development of algorithms and methods for interpretation and modelling of laser scanner data, resulting in useful

Laser scanners and laser scanner data

A laser scanning system produces data which can be characterised as sub-randomly distributed 3D point clouds. These point clouds may contain more information than a 2.5D surface model, in which the elevation has a unique z-value as a function of x and y. This means that vertical walls in certain cases can be seen as truly vertical, surface points beneath bridges can be measured and volumetric estimations of vegetation can be carried out. Elevation data can be acquired with different attributes

Processing of laser scanner data

The processing of laser scanner data often aims at either removing unwanted measurements, either in the form of erroneous measurements or objects, or modelling data given a specific model. Removing unwanted measurements, as in the case of finding a ground surface from a mixture of ground and vegetation measurements, is in this context referred to as filtering. The unwanted measurements can, depending on application, be characterised as noise, outliers or gross errors. Finding a specific

Discussion

The usefulness of airborne laser scanner systems has been shown by other authors in a number of applications where the generation of DEMs with traditional photogrammetric methods fail or become too expensive, e.g., DEMs over areas with dense vegetation (Kraus and Pfeifer, 1998) or 3D City Models (Haala et al., 1997). High quality DEMs with sampling distances of 0.25–2 m are provided, depending on the application and system, within a short time limit.

The limitation of laser scanner systems lies

Acknowledgements

Data and help provided by SAAB Survey Systems are highly appreciated.

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