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Semi-automatic 3D building extraction in dense urban areas using digital surface models. IMAGE. Dr. Philippe Simard President SimActive Inc. About SimActive. Founded in 2003, SimActive is the developer of Correlator3D™ software, a patented end-to-end photogrammetry solution
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Semi-automatic 3D building extraction in dense urban areas using digital surface models IMAGE Dr. Philippe Simard PresidentSimActive Inc.
About SimActive • Founded in 2003, SimActive is the developer of Correlator3D™ software, a patented end-to-end photogrammetry solution • SimActive has been selling Correlator3D™ to leading mapping firms and government organizations around the world • Correlator3D™ is the fastest commercial software to perform DSM generation due to the GPU DSM DTM Mosaic 3D Features
Correlator3D™ Software PROCESSING MODULES IMAGERY EO Refinement Satellite Aerial DSM Generation GeoEye Microsoft Ultracam DTM Extraction Worldview Intergraph Z/I DMC DEM Editing ALOS Prism Applanix DSS Cartosat-1 DiMAC Orthorectification Ikonos ADS80 Mosaic Creation Quickbird VM A3 Mosaic Editing SPOT Scanned Films Feature Extraction
Problem Definition Given Elevation models Need 3D Polygons describing 3D features Problem 3D buildings How to extract 3D features accurately and efficiently?
Existing Solutions Manual Fully Automatic Very slow collection process Fast High accuracy Error prone Require highly-trained personnel Significant editing required Automatically generated results do not meet user requirements Significant user interpretation required
Motivation • Customer feedback: • Simple buildings are easy – little time investment needed • Complex buildings are a challenge – no tools exist to handle these efficiently • Market gap: how to efficiently extract complex buildings? • 80% of the time is spent on 20% of the buildings • Key idea: design a novel approach for quick extraction of complex buildings
Our Approach • Semi-automatic • Requires simple feedback from user • Creates 3D polygons in 2D space using elevation models • 3D information is automatically extracted by intelligent analysis of the data
Workflow DSM Photogrammetric Optional LiDAR Visual Aid Mosaic 3D Polygons Buildings Water bodies Optional 2D / 3D Polygons Roads Building footprints Forestry Water body contours
Extracting Buildings How it works • User selects rough outline • Contour automatically fitted around building edges • 3D polygons created over the selectionusing elevation data in the DSM • Roof geometry is refined by segmenting the polygon into planes • Surfaces and edges are automatically merged in the background when appropriate
Buildings ContourExtraction Rough selection around building Contour fitted around building edges automatically
Buildings Roof Creation Original surface model Extracted contour First segment to add slope Vectorized building model Roof details added Final vector polygon
Visual Feedback • To help the operator, planes are automatically shaded in either red, yellow or green as roof geometry is refined • How it works: as the operator is segmenting the building polygon, the software automatically attempts to fit a plane over each new segment Red: Bad fit Yellow: Medium fit Green: Good fit
Buildings Advanced Functions • Best Fit: Uses elevation values surrounding selected planes to determine the best fit for these planes • Rectify: Aims to create right angles (90 degrees) between close-to perpendicular vectors • Merge Surface: Combines coplanar polygons automatically • Merge Edge: Remove redundant points
Sample Results Photogrammetric Input DSM Output building model Accuracy: 20cm resolution; 4cm vertical Accuracy: 10cm resolution; 10cm vertical
Sample Results LiDAR Input LiDAR DSM Output Vectors Accuracy: 1m resolution; 10 cm vertical Accuracy: 50cm resolution; 25cm vertical
Output Quality • Dependency: • Input DSM resolution / accuracy • User ability to correctly segment 3D surfaces during 3D feature extraction • Accuracy: • Horizontal: 0.5 times the GSD of DSM • Vertical: 2.5 times the vertical accuracy of DSM
Speed • Industry average: 30 seconds per complex building • SimActive average: 18 seconds per complex building Examples of complex buildings
Other Extraction Modes 3D features • Same technology has been adapted for other features • Forests • Roads • Water Bodies • Difference: how contours and 3D values are determined
Benefits • Fast collection process • High accuracy • Short learning curve • Best of both worlds solution
Future Developments • Image data will be used during editing to further increase accuracy • Automatic roof creation using templates • Extraction of other 3D shapes (e.g. spheres, cylinders) • 3D viewing
Thank You Dr Philippe Simard President SimActive Inc. Tel.: 514.288.2666 ext. 21 Fax: 514.288.6665 psimard@simactive.com www.simactive.com