This paper proposes a framework for generating bare-land Digital Elevation Model (DEM) in urban areas by combining highresolution satellite imagery and Airborne Laser Scanning (ALS) data. Airborne laser scanners offer an efficient approach for 3D data acquisition. ALS data provides very accurate position and height information, but less direct information on ground objects’ geometrical shape, meanwhile high-resolution satellite imagery such as IKONOS offers very detailed information on objects, such as spectral signature, texture, shape etc. Combining these two kinds complementary dataset is quite promising for the research of ground object recognition, e.g. building extraction, 3D city modeling etc. This paper presents the concept and procedures of the approach based on above idea, and also shows some experimental results.

Laser scanning provides structural and topographic detail previously unheard of. When conducting a LIDAR survey, however, it can be difficult or even impossible to collect measurements on all surfaces of a structure. Since LIDAR works under ‘line-of-sight’ principles, laser shadowing can be a significant issue. But since LIDAR sensors are available on several different platforms, sensor fusion can provide the means to generate complete, accurate solid models. Airborne laser scanners collect accurate georeferenced topographic data of large areas very quickly, while tripod-mounted laser scanners generate very dense, geometrically accurate data. Used in tandem, these scanners make it possible to generate complete solid models that are geometrically accurate on all surfaces. This paper documents the processing and fusing of airborne and tripod-mounted scanner data. The survey used an Optech Airborne Laser Terrain Mapper (ALTM) and an Optech ILRIS-3D laser scanner to survey Toronto City Hall in Toronto, Canada. The final product was a fused data set that represented the entire structure and its surrounding grounds.

Semi-automated object extraction has been established as a standard procedure for the efficient generation of 3D city models. Apart from aerial imagery, satellite imagery and laserscanner data turned out to be an additional source to create virtual city models. CyberCity-Modeler (CC-Modeler™) as a tool for the generation and optimisation of 3D city and plant models has been used in a range of projects with different requirements. Therefore modules have been developed and integrated to the main software package to improve functionality. CC-Modeler™ consists of four modules: CC-Modeler for topological structuring, CC-Edit for improving geometry , CC-Mapping for integration of wall texture and CC-Digit for integration of digitised data from maps. Concerning the software package CC-Modeler™, some functions as geometrical regularisation of buildings, editing functions for topology adjustment, modeling of overhanging roofs, adding attributes to objects, mapping from texture libraries, generation of corridors etc. are explained in this paper. Additionally, the use of satellite and laserscanner data for the efficient generation of 3D city models as an alternative or supplement to aerial images is discussed and the progress in real-time visualisation of 3D city models is presented.

Esta publicação quer contribuir para inserir a técnica do laser scanner aerotransportado no contexto brasileiro, trazendo informações relativas à técnica de obtenção de modelos digitais de terreno a partir dos dados gerados por este tipo de sensor. Seguindo o método chamado de pirâmide de imagens foi criado um filtro para imagens raster geradas a partir de dados de laser scanner aerotransportado. Os resultados obtidos ao processar imagens de alguns campos de teste na cidade de Karlsruhe (Alemanha) estão aqui apresentados.

Com o avanço da tecnologia, o Sensoriamento Remoto tem se tornado uma grande potência no estudo de áreas urbanizadas. Uma das novas ferramentas desenvolvidas nos últimos anos é laser scanning, que impulsionou o uso de sensoriamento remoto para o estudo e análise do ambiente urbano, pois possibilita a obtenção de informação altimétrica da cena, o que permite o reconhecimento de objetos, como prédios e vegetação. No entanto, o reconhecimento de objetos em este tipo de imagens demanda uma interpretação mais depurada, diferente da análise pixel a pixel convencional. Neste trabalho, foi utilizado o aplicativo eCognition é utilizado para efetuar a análise orientada a objeto de uma imagem de laser scanning. A área que a imagem altimétrica abrange é urbanizada, nela encontra-se edificações isoladas, pátios, ruas e áreas verdes. A análise deste trabalho se concentra numa classificação baseada na metodologia de dados orientados à objeto, considerando vários descritores (textura, forma, brilho etc) e numa classificação utilizando-se a lógica Fuzzy. Os resultados obtidos permitem uma comparação entre as duas análises realizadas, mostrando que é possível classificar uma imagem baseada em dados de altimetria, levando em consideração os vários descritores existentes para melhorar a eficiência da classificação realizada.

A new method for the automated generation of 3D building models from directly observed point clouds generated by LIDAR sensors is presented. By a hierarchic application of robust interpolation using a skew error distribution function, the LIDAR points being on the terrain are separated from points on buildings and other object classes, and a digital terrain model (DTM) can be computed. Points on buildings have to be separated from other points classified as off-terrain points, which is accomplished by an analysis of the height differences of a digital surface model passing through the original LIDAR points and a digital terrain model. Thus, a building mask is derived, and polyhedral building models are created in these candidate regions in a bottom-up procedure by applying curvature-based segmentation techniques. Intermediate results will be presented for a test site located in the City of Vienna.

In this article, two methods for data collection in urban environments are presented. The first method combines multispectral imagery and laser altimeter data in an integrated classification for the extraction of buildings, trees and grass-covered areas. The second approach uses laser data and 2D ground plan information to obtain 3D reconstructions of buildings. q1999 Elsevier Science B.V. All rights reserved.