Calibration of measurement bias of a barometric sensor in a wireless terminal

• US 10,367,932 B1
• Filed: 05/17/2018
• Issued: 07/30/2019
• Est. Priority Date: 04/05/2018
• Status: Active Grant

• Current Assignee: Polaris Wireless Incorporated
• Original Assignee: Polaris Wireless Incorporated
• Inventors: Zhu, Jian, Blaha, Jr., Jerome Arthur, Gordon, Scot Douglas, Lu, Jonathan Shiao-en, Wu, Jeffrey Noel
• Primary Examiner(s): Tran, Khoi H
• Assistant Examiner(s): Hannan, B M M
• Application Number:
  US15/982,726
• Time in Patent Office: 439 Days
• Field of Search: 4554561-457
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: G01C 5/06 by using barometric means
• CPC Class Codes: H04L 67/52 specially adapted for the location of the user terminal
• CPC Class Codes: H04M 1/24 Arrangements for testing
• CPC Class Codes: H04M 1/724 User interfaces specially adapted for cordless or mobile telephones
• CPC Class Codes: H04M 1/72403 with means for local support of applications that increase the functionality
• CPC Class Codes: H04M 1/72454 according to context-related or environment-related conditions
• CPC Class Codes: H04M 1/72457 according to geographic location
• CPC Class Codes: H04M 2250/12 including a sensor for measuring a physical value, e.g. temperature or motion telephones including GPS signal receivers H04M2250/10
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 4/025 using location based information parameters
• CPC Class Codes: H04W 4/38 for collecting sensor information
• CPC Class Codes: H04W 4/90 Services for handling of emergency or hazardous situations, e.g. earthquake and tsunami warning systems [ETWS]
• CPC Class Codes: H04W 88/02 Terminal devices

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.

Claims

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, 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.

2. The method of claim 1 further comprising transmitting the estimate of elevation of the first wireless terminal to a location-based application server.

3. The method of claim 1 wherein the identity of the first base station is in the form of at least one of a service set identifier (SSID) and a media access control (MAC) address.

4. The method of claim 1 further comprising:

receiving, by the data processing system, an identity of a second base station as reported by both i) the first wireless terminal and ii) a second wireless terminal that is at an elevation known to the data processing system;

receiving, by the data processing system, a third measurement of barometric pressure made by the first wireless terminal; and

generating a second estimate of bias of barometric pressure measured by the first wireless terminal, in part by comparing;

i) the third measurement of barometric pressure made by the first wireless terminal, to

ii) a true barometric pressure of a second building floor at a height that corresponds to the elevation known to the data processing system, wherein the true barometric pressure of the second building floor is derived from the height of the second building floor.

5. The method of claim 4 wherein the second estimate of bias is further based on both the first wireless terminal and the second wireless terminal reporting a radio signal transmitted by the second base station as exceeding a predetermined threshold.

6. The method of claim 1 further comprising:

adjusting the estimate of the elevation of the first wireless terminal, resulting in an adjusted estimate of elevation, in part by comparing the estimate of the lateral location of the first wireless terminal to a boundary of a building in a geographic information system (GIS) database; and

generating a second estimate of bias of barometric pressure measured by the first wireless terminal, in part by comparing;

i) the second measurement of barometric pressure made by the first wireless terminal, to

ii) a true barometric pressure of a second building floor at a height that corresponds to the adjusted estimate of elevation, wherein the true barometric pressure of the second building floor is derived from the height of the second building floor.

7. The method of claim 1 wherein the pressure reference is at an outdoor location.

8. The method of claim 1 wherein the estimate of the elevation of the first wireless terminal is further based on a generated series of more than one estimate of bias of barometric pressure measured by the first wireless terminal, wherein the series comprises the first estimate of bias of barometric pressure, and wherein the first estimate of bias of barometric pressure is weighted according to its relative age in the series.

9. The method of claim 1 wherein the height of the first building floor is information provided from a database.