Global positioning and image processing pinpoint locations

Global positioning and image processing pinpoint locations

Andrew Wilson

Accurate imaging information dealing with the positioning, identification, and location of highways, streets, and roads used to involve complicated image-processing tasks that required the collection and storage of vast quantities of data. Now, however, by integrating sophisticated global positioning systems (GPSs), inertial navigation systems (INSs), and off-the-shelf imaging components, the exact sitings of roadside identification points are becoming readily available.

For example, the GPSVision mapping system from Lambda Tech International (Waukesha, WI) integrates a 7400 dual-frequency GPS from Trimble (Sunnyvale, CA), a LN-200 INS from Litton (Woodland Hills, CA), and a personal-computer-based image-processing system. The resultant system can collect digital images along all types of roads and streets.

In operation, stereo images of the target road object are captured by a pair of progressive-scan charge-coupled-device cameras and then digitized by PC-based Power Grabber boards from Dipix (Ottawa, Ont. Canada). By digitizing the stereo images with a known position and direction capability provided by the integrated GPS/INS system, every target-object characteristic digitized by the two cameras is computed and translated into latitude, longitude, and height information.

However, because of its 1-kHz data rate, the use of the GPS alone is limited. Similarly, the INS provides accurate position and direction information, but sensor errors emerge over time. "Accurate GPS positioning is used to update the INS," says Dick Hammersley, vice president of Lambda Tech. "The INS then produces accurate position and directional data even when the GPS signals are lost."

To position visible features such as curb lines, traffic signs, manholes, and buildings, the system uses Lambda`s feature-extraction software. During use, the operator points at the object features of interest with the stereo-image camera pair, and the software triangulates the relative position of the selected feature and transfers it to a global co-ordinate system. Running under Windows 3.1, NT, 95, the software allows operators to select, control, and display images. A separate map window displays the tracking of the system, the image location, and the extracted features. For more information, contact Dick Hammersley at (414) 523-1215.