The Rosum Corporation of California has worked out how to use digital television to help a GPS receiver calculate its position faster (WO 03/043323). GPS receivers compare clock signals from four satellites to compute a position. But atmospheric conditions can introduce delays which require a correction signal calculated by a ground station. Receiving these ultra-low-power correction codes accurately via satellite takes considerable time, wasting receiver battery power.
Rosum’s answer is for the ground station to feed the correction codes to a TV broadcaster, which embeds it in an unseen portion of a powerful digital TV signal. A GPS receiver hears this loud and clear –…
