IMAGE Dense DSMs from Stereo Imagery 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  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 DSMDTMMosaic3D Features

Correlator3D™ Software DSM Generation EO Refinement Mosaic Creation DEM Editing Orthorectification DTM Extraction Microsoft Ultracam Applanix DSS DiMAC Intergraph Z/I DMC VM A3 Mosaic Editing PROCESSING MODULES IMAGERY ADS80 Scanned Films Aerial GeoEye ALOS Prism Cartosat-1 Worldview Quickbird Ikonos SPOT Satellite Feature Extraction

DSM Generation  A Digital Surface Model (DSM) is a representation of ground topography  Main Processing Steps:  1. Correlation  2. Triangulation  Bottom-up approach What is it? DSM Example

TriangulationCorrelation Focal point Image 1Image 2 Epipolar Traditional approach: How does it work? DSM Generation

DSM What is it?  A dense DSM has a grid post spacing approaching the ground sampling distance (GSD) of the input imagery Dense DSM Generation SimActive has just released its next generation DSM engine capable of producing dense DSMs Dense DSM

Challenges 1. Correlation 2. Sensitivity 3. Density  Process more difficult  Radiometry differences between images  Camera calibration  Exterior orientation  More points leads to longer processing time For dense DEM generation

 Bottom-Up  Derive solution  Feature-Based  High density in some areas only  CPU  Few cores Comparison Traditional  Top-Down  Test solutions  Grid-Based  High density in all areas  GPU  Hundreds of cores SimActive

Focal point Image 1Image 2 Top-Down Idea: test solutions and check whether they solve the correlation problem

Grid-Based Grid-based DEM is dense everywhere  No interpolation  Correlation performed on all points in the grid  Adjacent solutions assist each other

GPU Possible Solutions Processing Results P 11 P P n1 P 12 P P n2... P 1n... P 2n...P nn GPU Cores These solutions are processed by the GPU simultaneously When a match is found, the problem is solved 1 23 Many possible solutions are prepared to be tested 1 2 3

Results Resolution: 25 cm Accuracy: 5 cm Resolution: 15 cm Accuracy: 5 cm Dense DSM DSM

Benefits  World’s fastest commercially available DSM engine  Direct DSM result removing the need to convert from a point cloud  More points in low texture areas  DSM precision is consistent and homogeneous Dense DSM

Applications

Dr Philippe Simard President SimActive Inc. Thank You Official Reseller Groupe SCE India Mahesh Nagendra J Mobile: