Visual Odometry David Nister, CVPR 2004 2005. 1. 4 Computer Vision Lab. Young Ki Baik
Contents Introduction Algorithm Experimental results Conclusion and opinion.
Introduction Visual Odometry Features for real-time Usage of visual information as a sensor Realization of the real-time navigation system using 3D reconstruction algorithms (camera motion estimation algorithm) Features for real-time Parallel processing based PC (MMX) Pentium III 1GHz Fast algorithm Preemptive RANSAC (ICCV2003) Features for accuracy Stereo camera Calibrated framework
Introduction System overview Feature extraction 3D reconstruction Matching and tracking Motion estimation 5-point algorithm / P-RANSAC Triangulation method Bundle adjustment Harris corner detector Normalized correlation 3-point algorithm for 3D motion
Algorithm Feature extraction Harris corner detector No subpixel precision detection Usage of down sampled data (16 bit) Size of INT and FLOAT is 32 bit. Low size of data can be expected more efficiency for parallel processing. 32 bit MMX register 16 bit 64bit
Algorithm Feature matching … … … Normalized correlation over an 11x11 window 11x11 = 121 (for applying to 128 bit aligned memory) Matching with converted 1 dimensional vector using Parallel processing (MMX) is faster than normal method. Short search range (Video sequences have short base line) 121 7 Garbage space … Matching using MMX … …
Algorithm 3D reconstruction 5-point algorithm Only considering pose estimation. Usage of 2D points. Preemptive RANSAC (CVPR 2003) Fast RANSAC Triangulation method Conventional triangulation method is used for 3D reconstruction. Bundle adjustment Using small number of parameters and iteration.
Algorithm Motion estimation R, T 3-point algorithm Only considering camera pose (rotation and translation) estimation. Usage of 3D point. Generated points R, T Triangle Selected points
Algorithm Merit of using the Stereo Vision Known scale (baseline) Less affection by uncertainty in depth
R, T Algorithm The Stereo Scheme Triangulation Stereo camera Matching 3D motion (3-P algo., P-RANSAC) Matching Next frame Motion estimation (5-P algo., P-RANSAC) R, T Stereo camera Matching Triangulation
Algorithm The Stereo Scheme Firewall Optimization (LM) 3D motion estimation Certain number of frames Optimization (LM) Coordinate system is transferred. Firewall For stopping propagation error
Experimental results System configuration Experiments Environment CPU : Pentium III 1GHz (MMX) Stereo camera (360*240*2) size / FOV : 50˚ / Baseline : 28 cm Experiments GPS : Location error test INS : Direction error test Environment Loop Meadow Woods
Experimental results Processing time Location error Direction error Around 13Hz Location error Direction error
Experimental results Performance Red line : Visual odometry Blue line : DGPS
Experimental results Performance Red : Visual odometry Blue : DGPS
Conclusion and Opinion. Real-time navigation system is implemented. Opinion There is no refinement scheme for solving closing loop problem. More fast result with Pentium-IV (SSE2) There is room for improvement.