GPS/barometry height-aided positioning system

Shell Canada and Pulsearch Navigation Systems of Calgary have developed an integrated real time differential GPS and barometry system, with the prime aim of significantly changing and improving the method of positioning and layout of Shell Canada´s land seismic surveys. This system currently provides real-time horizontal accuracy to better than 5 metres, and vertical to better than 2 metres (2 sigma) and fills a significant niche in the survey market because of its design specification and low cost. Among these design criteria is the ability to provide this accuracy in rugged, heavily forested environments in which GPS has often not been viable due to terrain masking, signal degradation and loss under thick forest canopy, and general cost effectiveness. This enables surveys to be performed with little or no line cutting, which significantly reduces environmental impact, hazard exposure, and cost. Digital barometers are used to both accurately determine the elevations of seismic source and receiver locations, and to provide additional weighted height observations to a real time 3D differential GPS solution, thus significantly improving horizontal position accuracy and operating tolerance. The Magnavox GPS hardware and software have provided superior tracking performance under tree cover, compared to other hardware tested. The real time aspect of the system makes it a viable tool for line layout, surveying, and any other operational aspect that requires instantaneous knowledge of precise location