Center for Mapping

Introduction

Direct georeferencing of imaging sensors by means of integrated GPS/INS has been in the spotlight in the surveying/mapping and remote sensing communities since the mid-nineties. One reason is that the primary driving force behind this process is a need to accommodate the new spatial data sensors, such as LIDAR or SAR (airborne systems). The second reason is that a substantial cost decrease, a possibility automation of data reduction, and a short turn-around time are the most attractive features offered by this technology. The Ohio State University has long been involved in MMS (Mobile Mapping System) system developments and currently is developing a dedicated system for precise (centimeter level) monitoring of highway center and edge lines. The prototype-positioning component of the system is based on a tight GPS/INS coupling, and the imaging component comprises a single down-looking, high-performance color digital camera. The main features of the system are the high image capture rate, the online use of navigation estimates, and the on-the-fly image and stereo data processing.

From a navigation standpoint, the post processing of GPS/INS data provides more accurate orientation as a benefit of forward and backward trajectory processing and precisely synchronized timing information. However, some navigation data available in real-time (such as relative image orientation) can efficiently support the processing of the image sequences on-the-fly by extracting and storing only the necessary information, as opposed to the entire image (if only simple features, such as linear objects are needed). Obviously, further post-processing can rectify the positioning and orientation data that should subsequently be used to provide precise georeferencing to the features extracted in real time. This procedure adds more robustness to the system, allowing faster and more automatic data processing, saves storage space and processing time, as data acquisition can be combined with the image pre-processing.

The high-accuracy GPS/INS/CCD system designed for monitoring linear highway features is based on the concept of tight sensor integration, combining post-processing with real-time image processing.

 This project is sponsored by the Ohio Department of Transportation.

Introduction| System design| Hardware Implementation| Performance of the Automated Image Sequence Processing| Positioning Performance