Digital Terrain Model generation using airborne LiDAR in a forested area of Galicia, Spain

Luis Gonçalves-Seco, David Miranda, Rafael Crecente and Javier Farto
Land Laboratory – Department of Agroforestry Engineering
University of Santiago de Compostela – Campus universitario s/n, Lugo 27002, SPAIN
Tel.: + 34 982252231 Fax: + 34982285926
lgseco@usc.es; dmiranda@usc.es; rcrecente@usc.es; jfarto@usc.es

Abstract
Information on the shape and relief of the Earth’s surface is essential for improving land management practices that promote more  sustainable development. Such a need for information is even greater in regions with rough topography and a high percentage of woodland cover. In the last few years, Airborne Laser Scanning (ALS) technology has demonstrated that laser altimetry is a reliable technology for determining accurate Digital Terrain Models (DTM). This paper presents a method for filtering LiDAR data based on mathematical morphology that is capable of using point cloud data from both the first and last return to discriminate terrain points and to segment the objects in forested areas into low and high vegetation. A pilot project was conducted in a mountainous area of 4 km2  covered by Eucalyptus globulus plantations. In the study area, 4 zones were differentiated according to land use in order to allow for better presentation and interpretation of results. To validate the results, more than 40 control plots were distributed over the study area. In general, the results obtained in the study were better than expected, considering the hilly nature of the study area, often covered by dense shrub layers. RMSE values in the range 0.12 m – 0.27 m were obtained for the different zones studied, which reveals the suitability of the method for this type of data and this area. The inclusion of the first and last returns enabled an average increase of 27% in the number of terrain points, and guaranteed a final point density of 2 points/m2  before interpolation.

Keywords: airborne laser scanning, filtering, DTM, segmentation

In: Caetano, M. and Painho, M. (eds). Proceedings of the 7th International Symposium on Spatial Accuracy Assessment in Natural Resources and Environmental Sciences, 5 – 7 July 2006, Lisboa, Instituto Geográfico Português

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