Patent ID: 9681408
Date: 2017-06-13
CPC Classifications: G01S,G04R,H04W

Claim:
1. A method, for a movable device having a local clock, of determining a drift between the local clock and a reference clock that is used by one or more reference devices, by observing one or more signals transmitted by the respective one or more reference devices, the method comprising: when the movable device is at a calibration location, receiving at the movable device, at a first time, a first portion of the signal transmitted by one of the reference devices; moving the movable device to an operating location; and when the movable device is at the operating location, receiving at the movable device, at a second time, a second portion of the signal transmitted by one of the reference devices, the first portion and the second portion having been transmitted with a time-interval between them, according to the reference clock; the method further comprising: determining the time-interval; obtaining a model of the one or more signals, describing for each signal at least one of: determining local time information comprising: the first time and the second time, or a time difference between them, according to the local clock; defining position variables comprising: constructing a set of one or more equations, which relates the position variables, the model, the local time information, the time-interval, and the drift; solving the set of one or more equations, to determine the drift; and correcting the clock of the movable device based on the determined drift.