Continuous Navigation Combining GPS with Sensor-Based Dead Reckoning

摘要

"Can you hear me now?" This familiar question is asked countless times each day by mobile phone users attempting to improve their signal.Terrain, buildings, and foliage can block or seriously impede the propagation of cell-phone signals. Users of GPS receivers suffer the same problems. While there have been some advances in improving the sensitivity of GPS receivers and developing techniques such as assisted GPS that permit a GPS receiver to use attenuated signals, the antenna of a conventional receiver must have a direct line of sight to the GPS satellites. In urban canyons, it may not be able to "see" a sufficient number of satellites with good geometry to determine a three-dimensional position fix. And in tunnels or in parking garages, the receiver will see no satellites at all. Consequently, continuous navigation in many cities is impossible for conventional GPS-only navigation systems. In this month's column, we look at how GPS can be combined with other sensors to provide continuous navigation in even the most-challenging environments.