Test Results of Real Time Mapping of Roadways Using the GIM System

James LaMance, Randy Silva and Alison Brown

Abstract:	Global Position System (GPS) offers a quick and accurate method for establishing the mapping information required for a Geographic Information System (GIS) database. A significant problem in the gathering of mapping information using GPS is the gaps in the base map database caused by satellite shadowing, which may not be discovered until after the survey is complete. Gaps may also exist in the GIS attribute database because items were missed during the survey. These are costly problems that usually require new surveys to remedy. To address this problem the GPS/Inertial Mapping (GIM) system has been developed and can deliver l-2 meter accuracies in real time even in the event of temporary GPS signal loss. The GIM system combines differential GPS, inertial sensors, and position synchronized video to provide a powerful tool for generating precise, high quality mapping databases. This paper will describe GPS mapping sessions conducted in cooperation with the GIS Department of Douglas County Colorado using the NAVSYS GIM system. The roadways of Douglas County offer an ideal geography to test the capabilities of the NAVSYS GIM system because it offers both urban and rural sections where the GPS signals can be blocked by obstructions that vary from buildings to mountain canyons. The paper will include the test data collected during the mapping sessions and will demonstrate why inertial aiding is an important component for mapping instrumentation. The paper will also present the results of an independent evaluation of the GIM System conducted by The Ohio State University Center for Mapping. The NAVSYS GIM system incorporates an innovative optimal processing algorithm that enhances the performance of the GPS/Inertial navigation. This approach enables a low cost Inertial Measurement Unit (IMU) to be employed in combination with a GPS receiver, and the John E. Chance Omnistar wide area differential GPS correction system to provide an accurate, real time position and attitude reference. The overall process is controlled by an intelligent data management system capable of recording feature and attribute information in real time, with associated time tagging for exact location tagging, in both video and electronic formats. The GIM system is packaged into a portable, modular architecture that is suited for various vehicles such as cars, four wheel drives, watercraft, or railroad cars, allowing quick and accurate surveys to be performed in a wide variety of geographies. In addition, a variety of GPS receivers, differential GPS receivers, and IMUs are supported.
Published in:	Proceedings of the 52nd Annual Meeting of The Institute of Navigation (1996) June 19 - 21, 1996 Royal Sonesta Hotel Cambridge, MA
Pages:	765 - 770
Cite this article:	LaMance, James, Silva, Randy, Brown, Alison, "Test Results of Real Time Mapping of Roadways Using the GIM System," Proceedings of the 52nd Annual Meeting of The Institute of Navigation (1996), Cambridge, MA, June 1996, pp. 765-770.
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