Abstract:
A positioning system operates by first determining that a user is pedestrian, and then estimating a speed of the user. Having tracked a first signal from one radio transmitter whose position is known, the system attempts to detect additional signals from the one transmitter, in a search space such that the first signal and the or each additional signal are consistent with the estimated speed of the user and with one or more of the signals having been reflected off a reflector in the vicinity of the user. One or more detected additional signals from the one transmitter are then tracked, and candidate measurements, derived from the first signal and the one or more detected additional signals, are provided for use when estimating the position and/or velocity of the user.
Abstract:
A positioning system obtains an estimate of the heading of a body whose position or velocity is to be estimated, for example from a heading sensor such as a gyroscope or accelerometer. Respective signals are tracked from a plurality of transmitters, and a respective Doppler measurement is obtained from each of said tracked signals. For each of the tracked signals, a speed of the body is estimated using the estimate of the heading of the body and the respective Doppler measurement. It is then determined whether the estimated speed of the body is consistent with the signal having been received along a direct path from the transmitter. Signals that provide information about the speed of the body that is inconsistent with the signal having been received along a direct path from the transmitter are then disregarded when estimating the position or velocity of the body.
Abstract:
A position determining system takes the form of a cellular radio system including at least one base station having a base station satellite receiver (6) and a mobile unit including a cellular mobile station (50) coupled to a local satellite receiver (58). The base station transmits base station satellite data via a cellular radio link to the mobile unit, the data including data representing a carrier phase measurement derived from a satellite signal (70) received by the base station satellite receiver (6). The mobile unit determines its position relative to the base station using local satellite data received by the local satellite receiver (58) and corrects errors in this position determination using base station satellite data. The relative positions of the base stations are determined automatically with reference to an external positional reference which may be a satellite-based position determining system.