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:: RAY TRACING AND SAR-TOMOGRAPHY FOR 3D ANALYSIS OF MICROWAVE SCATTERING AT MAN-MADE OBJECTS S. Auer, X. Zhu, S. Hinz, R. Bamler

Document type:: Monograph

Structure type:: Chapter

CMRT09: Object Extraction for 3D City Models, Road Databases and Traffic Monitoring - Concepts, Algorithms, and Evaluation 160 • slice no. 3 for displaying intensities in elevation direction According to the defined slices, necessary data in slant-range, azimuth and elevation are extracted out of the data pool provided by the sampling process in POV Ray. Slant Range |m| Figure 5: Slice 1: elevation heights in slant-range direction (slice 1 in Figure 4 corresponds to slant range interval 60 m to 140 m); blue: single bounce contributions, green: double bounce contributions -40 -30 -20 -10 O 10 20 30 40 Azimuth [mj Figure 6: Slice 2: elevation information along azimuth direction displayed in height over ground; blue: single bounce contributions, green: double bounce contributions; zero level = level of ground surrounding the step Since the incidence angle used for sampling the 3D model scene is known, slice no. 1 pointing in slant range direction can be presented by two versions, either by displaying elevation heights (Figure 5), i.e. elevation coordinates with respect to a master height situated in the center of the image plane used for sampling the scene, or by providing height information in height over ground geometry, i.e. heights with respect to the ground surrounding the box. Following the slant-range direction from left to right, displaying height data in elevation heights enables to distinguish between range intervals containing one scatterer and areas containing several scatterers resulting in layover effects, which can not be separated in reflectivity maps such as shown in Fig. 3 (right). In Figure 5, reflection caused by direct backscattering are colored in blue color while double bounce contributions are indicated by green spots. Due to the incidence angle of 45 degrees, double bounce effects are focused at the same position in slant- range and are overlaid by both single bounce contributions at the ground and single bounce contributions reflected at the end of the step up-side. Following slice no. 2 along its way, elevation information is shown along the azimuth direction in height over ground (Figure 6). After passing an interval of contributions directly backscattered at the ground, the layover region starts showing the width of the double bounce areas in azimuth, which are equal to the width of the step model. As expected, double bounce contributions caused by the interaction between perpendicular faces are concentrated at the corresponding intersection lines and, hence, show a height value of 0 and 20 meters, respectively. Figure 7: Slice 3: normalized intensities along elevation direction; step width in elevation: 2 meters; blue: single bounce contributions, green: double bounce contribution Slice no. 3 pointing in elevation direction is shown in Figure 7. After the spatial sampling along elevation direction is chosen by the operator, intensity contributions are assigned to elevation intervals and summed up. Since the selected pixel is located within the double bounce area of two dihedrals, slice no. 3 shows two strong double bounce contributions caused by the interaction of step faces (colored in green) accompanied by weak direct backscattering derived at the step faces (colored in blue). Although the radiometric quality of detected intensity contributions is moderate due to simplified reflection models and the approximation of SAR signals by rays, proportions between single and double bounce intensities within one resolution cell are well represented. In the following Section, simulation results will be compared to real data derived by tomographic analysis. 3. COMPARISON: SIMULATION VS. REAL DATA For demonstrating potential applications of SAR simulation in elevation dimension, a practical example extracted from tomographic analysis using TerraSAR-X high resolution spotlight data is provided in this section and compared to simulation results. 3.1 Object modelling Fig.8 shows the 2D intensity map for the convention center of Las Vegas acquired by TerraSAR-X. For the purpose of this paper, an azimuth-range pixel marked by a green dot has been taken as example. The complex valued measurement at this pixel corresponds to the integration of the reflected radar signal

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