Abstract
Abstract. Recent advances in positioning techniques have made it possible to develop Mobile Mapping Systems (MMS) for detection and 3D localization of various objects from a moving platform. On the other hand, automatic traffic sign recognition from an equipped mobile platform has recently been a challenging issue for both intelligent transportation and municipal database collection. However, there are several inevitable problems coherent to all the recognition methods completely relying on passive chromatic or grayscale images. This paper presents the implementation and evaluation of an operational MMS. Being distinct from the others, the developed MMS comprises one range camera based on Photonic Mixer Device (PMD) technology and one standard 2D digital camera. The system benefits from certain algorithms to detect, recognize and localize the traffic signs by fusing the shape, color and object information from both range and intensity images. As the calibrating stage, a self-calibration method based on integrated bundle adjustment via joint setup with the digital camera is applied in this study for PMD camera calibration. As the result, an improvement of 83 % in RMS of range error and 72 % in RMS of coordinates residuals for PMD camera, over that achieved with basic calibration is realized in independent accuracy assessments. Furthermore, conventional photogrammetric techniques based on controlled network adjustment are utilized for platform calibration. Likewise, the well-known Extended Kalman Filtering (EKF) is applied to integrate the navigation sensors, namely GPS and INS. The overall acquisition system along with the proposed techniques leads to 90 % true positive recognition and the average of 12 centimetres 3D positioning accuracy.
Highlights
Mapping Systems (MMS) integrates imaging sensors and the navigation ones in order to provide the geo-spatial data of remotely sensed points from a mobile platform
Unlike other systems, which use Laser scanners or/and multiple digital cameras, the developed MMS comprises one range camera based on Photonic Mixer Device (PMD) technology and one standard 2D digital camera
Our proposed calibration method achieved 25% and 36% improvement on RMS of range error and coordinate residual, respectively, over that obtained by integrated calibration of the single PMD camera
Summary
MMS integrates imaging (mapping) sensors and the navigation ones in order to provide the geo-spatial data of remotely sensed points from a mobile platform. As a proposed solution to these problems, this study overviews the implementation and evaluation of an operational MMS for detection, recognition and 3D localization of traffic signs. This project has been performed under the collaboration of the University of Tehran and the University of Isfahan. This new generation of active devices can capture range, amplitude and intensity images simultaneously with one array sensor at video rates They have several advantages in comparison with traditional 3D data acquisition systems such as laser scanners or stereo cameras.
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