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Improving laser scanning quality, especially in urban environments

The project deals with factors affecting the total quality of laser scanning surveys, in particular for urban environments, with a view to improving methods and software, and calibrating and integrating image and laser data.

The project has the following research and business objectives: RESEARCH OBJECTIVES 1) Analysis of the quality of laser scanning and analysis of the factors affecting the quality. 2) In-flight calibration of Light Detection And Ranging (LIDAR) systems. 3) The use of image information to assist products developed mainly on the basis of airborne laser data. BUSINESS OBJECTIVES 1) Development and improvement of methods and software tools for laser scanning data processing based on R&D work within the project. 2) To increase the global market share and turnover of the TerraScan software. Presently, the TerraScan is assumed to be the global market leading software concerning laser-scanning processing. It is used by the majority of the users of the major laser data providers such as OPTECH, L/H and TOPEYE. TERRASOLID OY has programmed TerraScan, mainly by one talented software specialist, Arttu Soininen. TERRASOLID's turnover increased by 40 % during the last year, mainly due to the TerraScan software product. The global use of laser scanning is increasing at an incredible speed and reliable, user-friendly software, which is based on research findings, is needed. Several methodological and algorithmic improvements are performed for TerraScan by TERRASOLID. The quality of the improvements is tested by experiments. The FINNISH GEODETIC INSTITUTE (FGI) has a large number of exact reference points in a joint test with the HESLINKI UNIVERSITY OF TECHNOLOGY (HUT) campus area (surveyed with TOPEYE in September 2002). Some examples of improvements are the adjustment of laser strips, smoothing of surfaces, and use of laser-based breaklines. In order for such a small company to develop the TerraScan software, good networking with research organisations and good access to research findings are necessary. In order to support the technological development of TerraScan, the research consortium has established 3 joint objectives (listed above) with a high degree of innovation. The research objectives are described here in detail. Research Objective 1: The quality of laser scanning is a complex problem due to a wide variety of sensors and their parameters. In the analysis of quality, the emphasis is put on the analysis of factors affecting quality. The factors to be studied are: - type of target (asphalt, concrete, grass, wood, etc.) - sensitivity of target and DEM models for outliers - use of original cloud of points versus the use of surface models and smoothed surfaces * use of first and last pulse and intensity information * the effect of applied sensors (TOPOSYS, TOPEYE, OPTECH) * the effect of flight altitude, scan angle, incidence angle and measurement geometry * pulse density * the effect of the slope of the DEM. This work will be coordinated by the FINNISH GEODETIC INSTITUTE. 3-D models of city areas are becoming more and more important for various kinds of detailed planning, e.g. cellular network planning. Therefore, the project will concentrate mainly on the quality of city areas. The project is the first project to deal with factors that affect laser scanning quality at an international level. Research Objective 2: The INSTITUT CARTOGRAPIC DE CATALUNYA (ICC) has developed an automatic procedure for the adjustment of laser strips and a flight methodology. TERRASOLID and ICC methodologies will be compared and hopefully a new improved method will be proposed. Some parameters of LIDAR systems must be evaluated in in-flight calibrations. There is no standard or accepted procedure to perform this calibration. Different methods are used, but all of them are incomplete and approximate and have a strong impact on the precision of the results. An analysis and comparison of the different approaches could be conducted in order to propose a standard procedure. Research Objective 3: Image information (radiometric and geometric) and their derived products can help us interpret airborne laser information. By working on a test area including digital images and airborne laser data, it would be very interesting to study the following aspects: - Comparison between the techniques: statistical evaluation of both laser and correlation Digital Surface Model (DSM) - Setting up laser data: photogrammetric DSM products could be useful to improve this topic - Filtering of airborne laser data: correlation DSM could guide the user to skip objects above the ground (buildings and vegetation) - Use of radiometric information to reduce the blindness of the airborne laser systems: 3-D laser points could be back projected upon several available images to collect some radiometric information and thus allow an easier interpretation of laser data. The integration of laser scanner data and image data is the major technological breakthrough that has to be developed during this century. Currently, this kind of work is in its early stages. Basics of laser scanning: A laser scanner survey provides a cloud of points, the x, y and z coordinates of which are known. They form a Digital Surface Model (DSM), which includes e.g. terrain points, vegetation points, and points reflected from buildings. By processing the data and classifying the points as terrain and vegetation points, it is possible to produce various kinds of 3-D surfaces representing terrain and target properties. This knowledge can be used for a large number of applications, ranging from 3-D city models to characterisation of individual tree canopies. Laser scanning became better known in the mid-90s, and since then the technology has developed rapidly. MILESTONES * Month 1: kick-off of the project, partners meeting - description of the data to be used for the work. * Month 5 - all data should be available for the project. * Month 12, partners meeting - Quality of the laser scanning and factors affecting it should be ready. * Month 16 - Calibration and integration of image and laser data should be ready. * Month 18, partners meeting - major changes implemented in TerraScan. * Month 20 - final reporting and cost report. Keywords: quality, laser scanning, accuracy.
Acronym: 
LASCAN_QUALITY
Project ID: 
3 018
Start date: 
01-05-2003
Project Duration: 
24months
Project costs: 
500 000.00€
Technological Area: 
Optical Technology related to measurements
Market Area: 

Raising the productivity and competitiveness of European businesses through technology. Boosting national economies on the international market, and strengthening the basis for sustainable prosperity and employment.