Calibration of measurement bias of a barometric sensor in a wireless terminal
First Claim
1. A method of estimating the elevation of a first wireless terminal, the method comprising:
- receiving, by a data processing system, an identity of a first base station as reported by the first wireless terminal;
receiving, by the data processing system, a first measurement of barometric pressure made by the first wireless terminal;
receiving, by the data processing system, a measurement of barometric pressure made by a pressure reference;
generating a first estimate of bias of barometric pressure measured by the first wireless terminal, in part by comparing;
i) the first measurement of barometric pressure made by the first wireless terminal, toii) a true barometric pressure of a first building floor, wherein the first building floor is the building floor of the first base station whose identity is reported by the first wireless terminal, and wherein the true barometric pressure of the first building floor is derived from a) the measurement of barometric pressure made by the pressure reference and b) the height of the first building floor;
receiving, by the data processing system, a second measurement of barometric pressure made by the first wireless terminal;
obtaining an estimate of a lateral location of the first wireless terminal; and
generating an estimate of the elevation of the first wireless terminal based on;
(i) the estimate of the lateral location of the first wireless terminal,(ii) the second measurement of barometric pressure made by the first wireless terminal, and(iii) the first estimate of bias.
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Accused Products
Abstract
A location engine that estimates the barometric pressure measurement bias of a wireless terminal, resulting in an improved estimate of elevation of the wireless terminal. The location engine generates an estimate of measurement bias by comparing the barometric pressure measured by the wireless terminal while at that elevation and the barometric pressure that corresponds to an estimated elevation of the wireless terminal when it made the pressure measurement (i.e., the expected pressure). The estimated elevation is based on an inferred above-ground height and the local terrain elevation, and the expected pressure is based on the measurement of barometric pressure at the pressure reference and the estimated elevation. The location engine infers the height based on various techniques disclosed herein. The location engine can use the measurement bias to adjust subsequent pressure measurements reported by the wireless terminal, in order to generate an improved estimate of elevation of the wireless terminal.
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Citations
9 Claims
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1. A method of estimating the elevation of a first wireless terminal, the method comprising:
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receiving, by a data processing system, an identity of a first base station as reported by the first wireless terminal; receiving, by the data processing system, a first measurement of barometric pressure made by the first wireless terminal; receiving, by the data processing system, a measurement of barometric pressure made by a pressure reference; generating a first estimate of bias of barometric pressure measured by the first wireless terminal, in part by comparing; i) the first measurement of barometric pressure made by the first wireless terminal, to ii) a true barometric pressure of a first building floor, wherein the first building floor is the building floor of the first base station whose identity is reported by the first wireless terminal, and wherein the true barometric pressure of the first building floor is derived from a) the measurement of barometric pressure made by the pressure reference and b) the height of the first building floor; receiving, by the data processing system, a second measurement of barometric pressure made by the first wireless terminal; obtaining an estimate of a lateral location of the first wireless terminal; and generating an estimate of the elevation of the first wireless terminal based on; (i) the estimate of the lateral location of the first wireless terminal, (ii) the second measurement of barometric pressure made by the first wireless terminal, and (iii) the first estimate of bias. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification