CMRT09

Stilla, Uwe

Bibliographic data

Monograph

Persistent identifier:: 856955019

Author:: Stilla, Uwe

Title:: CMRT09

Sub title:: object extraction for 3D city models, road databases, and traffic monitoring ; concepts, algorithms and evaluation ; Paris, France, September 3 - 4, 2009 ; [joint conference of ISPRS working groups III/4 and III/5]

Scope:: X, 234 Seiten

Year of publication:: 2009

Place of publication:: Lemmer

Publisher of the original:: GITC

Identifier (digital):: 856955019

Illustration:: Illustrationen, Diagramme, Karten

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Monograph

Collection:: Earth sciences

Chapter

Title:: SEMI-AUTOMATIC CITY MODEL EXTRACTION FROM TRI-STEREOSCOPIC VHR SATELLITE IMAGERY F. Tack, R. Goossens, G. Buyuksalih

Document type:: Monograph

Structure type:: Chapter

In: Stilla U, Rottensteiner F, Paparoditis N (Eds) CMRT09. IAPRS, Voi. XXXVIII, Part 3/W4 — Paris, France, 3-4 September, 2009 SEMI-AUTOMATIC CITY MODEL EXTRACTION FROM TRI-STEREOSCOPIC VHR SATELLITE IMAGERY F. Tack a- *, R. Goossens a , G. Buyuksalih b d Dept, of Geography, Ghent University, Krijgslaan 281, 9000 Ghent, Belgium - (f.tack, rudi.goossens)@ugent.be b IMP-Bimtas, 34430 Beyoglu, Istanbul, Turkey - gbuyuksalih@yahoo.com KEY WORDS: Photogrammetry, City DSM generation, Tri-stereoscopy, Ikonos, Urban ABSTRACT: In this paper a methodology and results of semi-automatic city DSM extraction from an Ikonos triplet, is introduced. Built-up areas are known as being complex for photogrammetric purposes, mainly because of the steep changes in elevation caused by buildings and urban features. To make surface model extraction more robust and to cope with the specific problems of height displacement, concealed areas and shadow, a multi-image based approach is followed. For the VHR tri-stereoscopic study an area extending from the centre of Istanbul to the urban fringe is chosen. Research concentrates on the development of methods to optimize the extraction of a surface model from the bundled Ikonos triplet over an urban area, without manual plotting of buildings. Optimal methods need to be found to improve the radiometry and geometric alignment of the multi-temporal imagery, to optimize the semi-automatical derivation of DSMs from an urban environment and to enhance the quality of the resulting surface model and especially to reduce smoothing effects by applying spatial filters. 1. INTRODUCTION The high level of detail and geometric accuracy of very high resolution satellite data such as Ikonos imagery, has made this kind of imagery suitable for DSM generation at feature level of urban environments. Due to the photogrammetric complexity of urban areas, quite some research is done to cope with the specific problems of urban surface model generation from standard stereopairs. As a multi-image based approach can make the 3D modelling more robust, a methodology and results of semi-automatic DSM production from an Ikonos triplet over an urban area, is highlighted in this paper. From a theoretical point of view the redundancy of a third image should lead to a more reliable photogrammetric processing. Only a few investigations have been published dealing with the concerning subject. Research published in (Baltsavias et al., 2006) and (Raggam, 2006) can be referred to. Research is conducted within the framework of the MAMUD project (Measuring And Modelling of Urban Dynamics) funded by the STEREO (Support to The Exploitation and Research of Earth Observation data) program of Belgian Science Policy. The objectives of the MAMUD research project is to investigate the possibilities of earth observation for a better monitoring, modelling and understanding of urban growth and land-use change. Urban change processes are affecting the human and natural environment in a not unimportant way. This enlarges the need for more effective urban management approaches based on sustainable development. A sustainable urban management needs sufficiently detailed and reliable base information on the urban environment and its dynamics. Satellite imagery has proven to be an important data source to monitor and describe urban areas and its changes. Hereby, detailed information on the vertical structure is vital to label urban features, to describe urban morphology and to generate spatial metrics. If the subsequent approach is proved to be successful, it will increase the flexibility of producing semi-automatic 3D city models from high resolution satellite imagery. The complexity of an urban environment for photogrammetric purposes will be highlighted in section 2. In section 3 the image dataset and work area will be outlined. The different phases of the photogrammetric processing of the Ikonos triplet are stated in section 4. In following section, spatial filtering is applied on the height values of the surface model to improve the quality and reduce smoothing effects. Geometric accuracy analysis is discussed in section 6. Finally, in section 7 experiences and conclusions are summarized. 2. COMPLEXITY OF URBAN AREAS A Digital Surface Model is a digital representation of the terrain and topographic object height in a grid structure. Interpolation of the discrete height values is needed to approximate the continuity of the ground surface. Urban environments are experienced as complex for 3D modelling purposes because of the steep changes in elevation and the discrepancy between the smoothness of the ground surface and abrupt discontinuities caused by buildings and other urban features. Without manual plotting or spatial filter techniques it is difficult to reconstruct vertical walls out of VHR satellite imagery. An interpolation technique creates a smoothed surface and causes individual buildings will have a shape of a bell instead of the rectangular geometry (Jacobsen, 2006). A second consequence of steep changes in elevation is the occurrence of shadow and concealed areas. Due to the convergent viewing angle of VHR sensors like Ikonos, terrain features with certain height above the surface are geometrically displaced in the imagery, leading to dissimilarities between the stereo images. By this distortion of its true position, parts of the ground surface can be hidden in the satellite image. These are so-called occluded areas. Shadow areas, which have poor contrast, and Corresponding author

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