Patent ID: 9547067
Date: 2017-01-17
CPC Classifications: G01S

Claim:
1. A method of estimating the position of a user device comprising the steps of: at each of a plurality of measurement points of known position within a zone, scanning for electromagnetic signal sources of known position, obtaining and storing measurements of the strength of the signal received from the scanned electromagnetic signal sources, to thereby obtain measurements of the strength of the signal received from a plurality of electromagnetic signal sources at a plurality of measurement points within the zone; processing the stored data, the positions of the plurality of measurement points and the positions of the electromagnetic signal sources and, for each of the electromagnetic signal sources, fitting the measurements of received signal strength to a function of received signal strength with distance between the respective measurement point and the respective electromagnetic signal source, thereby obtaining parameters of the fitted function, the fitted function comprising as variables the received signal strength from the respective electromagnetic signal source and the distance between the respective measurement point and the respective electromagnetic signal source, the variables being related to each other by the parameters; for each of the electromagnetic signal sources, storing the parameters of the fitted function; and subsequently calculating the position of a user device by scanning for electromagnetic signal sources of known position, measuring the received signal strength from the scanned electromagnetic signal sources, retrieving the parameters of the function stored for the zone with reference to the scanned electromagnetic signal sources, using the function, the retrieved parameters and the received signal strengths measured by the user device to estimate the distance of the user device from each of the scanned electromagnetic signal sources; and estimating the position of the user device from the estimated distances from the scanned electromagnetic signal sources and the known positions of the electromagnetic signal sources.