In this paper, a number of techniques for segmentation and classification of airborne laser scanner data are presented. First, a method for ground estimation is described, that is based on region growing starting from a set of ground seed points. In order to prevent misclassification of buildings and vegetation as ground, a number of non-ground regions are first extracted, in which seed points should be discarded. Then, a decision-level fusion approach for building detection is proposed, in which the outputs of different classifiers are combined in order to improve the final classification results. Finally, a technique for building reconstruction is briefly outlined. In addition to being a tool for creating 3D building models, it also serves as a final step in the building classification process since it excludes regions not belonging to any roof segment in the final building model.
The ongoing technical developments on airborne laser scanner systems, with shorter pulses, increased operation
altitudes, focal plane array detectors, full-waveform digitization and recoding, etc. provide new opportunities for the
expansion and growth of military as well as civilian applications. However, for the continuing development of systems
and applications one crucial issue is the research and development of new and efficient laser data processing methods for
analysis and visualization.
In this paper we will present some recent developments on visualization and analysis of full-waveform data. We will
discuss visualization of waveform data by inserting the waveform samples in a 3D volume consisting of small 3D cells
referred to as voxels. We will also present an approach for extracting additional 3D point data from the waveforms. The
long term goal of this research is to develop methods for automated extraction of natural as well as man-made objects.
The aim is to support the construction of high-fidelity 3D virtual environment models and detection and identification of
man-made objects.
This paper wil give an overview of 3D laser sensing and related activities at the Swedish Defence Research Agency (FOI) in the view of system needs and applications. Our activites include data collection of laser signatures for target and backgrounds at various wavelengths. We will give examples of such measurements. The results are used in building sythetic environments, modellin of laser radar systems and as training sets for development of algorithms for target recognition and weapon applications. Present work on rapid environment assessment includes the use of data from airborne laser for terrain mapping and depth sounding. Methods for automatic target detection and object classification (buildings, trees, man-made objects etc.) have been developed together with techniques for visualisation. This will be described in more detail in a separate paper. The ability to find and correctly identify "difficult" targets, being either at very long ranges, hidden in the vegetation, behind windows or under camouflage, is one of the top priorities for any military force. Example of such work will be given using range gated imagery and 3D scanning laser radars. Different kinds of signal processing approaches have been studied and will be presented more in two separate papers. We have also developed modeling tools for both 2D and 3D laser imaging. Finally we will discuss the use of 3D laser radars in some system applications in the light of new component technology, processing needs and sensor fusion.
KEYWORDS: 3D modeling, Data modeling, Buildings, Systems modeling, RGB color model, LIDAR, Data processing, Laser systems engineering, Visual process modeling, Visualization
Detailed 3D environment models for visualization and computer based analyses are important in many defence and homeland security applications, e.g. crisis management, mission planning and rehearsal, damage assessment, etc. The high resolution data from airborne laser radar systems for 3D sensing provide an excellent source of data for obtaining the information needed for many of these models. To utilise the 3D data provided by the laser radar systems however, efficient methods for data processing and environment model construction needs to be developed. In this paper we will present some results on the development of laser data processing methods, including methods for data classification, bare earth extraction, 3D-reconstruction of buildings, and identification of single trees and estimation of their position, height, canopy size and species. We will also show how the results can be used for the construction of detailed 3D environment models for military modelling and simulation applications. The methods use data from discrete return airborne laser radar systems and digital cameras.
In this paper, a technique for generation of terrain elevation data for synthetic environments from laser-radar images will be demonstrated. The method is characterized by maintaining the high resolution that is available in source data without too much loss of significant information in its data reduction process. Separation of forest information as well as other types of outstanding objects from the ground is another important step in the process of generating a reliable terrain elevation model. As a consequence, it is possible to generate terrain models with a resolution of less than 0.5 m and where data have been highly reduced.
Recently a number of airborne nadir scanning laser radars have been developed for both military and civilian applications. These have range resolutions on the order of 10 cm but relatively moderate area coverage rates, in the range 1000 - 10,000 m2/s (3.6 - 36 km2/h) when operating in a high resolution mode with 0.25 m spot distance. Technology development in laser sources, scanning techniques and signal processing will probably improve the area coverage substantially and lead to compact systems suitable for new applications, including the use in UAV:s. Present nadir capability could be combined with a forward looking capability for guidance and obstacle avoidance in autonomous or semi-autonomous systems. The paper will investigate the potential performance of such combined systems using state-of-the-art lasers and receiver technology. Among the applications for both military and civilian users we note the collection of 3-D data for terrain modeling and object recognition. For these functions signal processing using multiple echo and intensity information is of great value as well as adding passive senor information. Full wave form processing will further improve the information for example to characterize trees. The use of high resolution 3-D data in synthetic environments is obvious and will be discussed. Experimental data collected with a commercial laser system, TopEye, developed by Saab Dynamics, will be shown and some image examples will be discussed in relation to different applications.
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