SYSTEMS AND METHODS FOR POSITIONING DURING ATYPICAL ATMOSPHERIC CONDITIONS
Determining when a barometric-based approach for estimating an unknown altitude of a mobile device should not be used. Different approaches determine if estimating an unknown altitude of a mobile device using a measured atmospheric condition will result in an estimated altitude having acceptable or unacceptable error. If use of the measured atmospheric condition would result in acceptable error, the measured atmospheric condition is used to estimate the unknown altitude. If use of the measured atmospheric condition would result in unacceptable error, the measured atmospheric condition is not used to estimate the unknown altitude. The resultant altitude estimate is then used to locate the mobile device.
1 . A method for determining an estimate of a currently unknown altitude of a mobile device, wherein the method comprises:
determining a location of the mobile device using location information;
measuring an atmospheric condition at the location of the mobile device using an atmospheric condition sensor of the mobile device;
detecting a first change of the measured atmospheric condition that exceeds a threshold value of change; and
in response to detecting the first change of the measured atmospheric condition, determining the estimate of the currently unknown altitude of the mobile device using an estimate of movement by the mobile device without using the measured atmospheric condition.
2 . The method of claim 1 , further comprising:
detecting a second change of the measured atmospheric condition that does not exceed the threshold value of change; and
in response to detecting the second change of the measured atmospheric condition, determining the estimate of the currently unknown altitude of the mobile device using the measured atmospheric condition as an input to a known barometric formula that is used to estimate altitude of the mobile device.
3 . The method of claim 1 , further comprising:
determining the estimate of the movement by the mobile device using an inertial sensor of the mobile device or using terrestrial or satellite ranging signals received by the mobile device from transmitters at known locations or a satellite system.
4 . The method of claim 1 , wherein:
the atmospheric condition sensor is a temperature sensor, a pressure sensor, a humidity sensor, or a gas sensor.
5 . The method of claim 1 , wherein:
the measured atmospheric condition is temperature, pressure, or air density.
6 . The method of claim 1 , wherein:
the estimate of movement by the mobile device is between a previously-determined estimate of a previously unknown altitude and the currently unknown altitude.
7 . A method for determining an estimate of a currently unknown altitude of a mobile device, wherein the method comprises:
determining a location of the mobile device using location information;
measuring an atmospheric condition at the location of the mobile device using an atmospheric condition sensor of the mobile device;
computing a first estimate of the currently unknown altitude of the mobile device using the measured atmospheric condition;
computing a second estimate of the currently unknown altitude of the mobile device without using the measured atmospheric condition;
detecting a first computed difference between the first estimate and the second estimate that exceeds a threshold difference of altitude; and
in response to detecting the first computed difference, determining the estimate of the currently unknown altitude of the mobile device using an estimate of movement by the mobile device without using the measured atmospheric condition;
wherein the second estimate is computed by using a previously-determined estimate of a previously unknown altitude of the mobile device and an estimate of movement by the mobile device between the previously unknown altitude and the currently unknown altitude.
8 . The method of claim 7 , further comprising:
detecting a second computed difference between the first estimate and the second estimate that does not exceed the threshold difference of altitude; and
in response to detecting a second computed difference, determining the estimate of the currently unknown altitude of the mobile device using the measured atmospheric condition as an input to a known barometric formula that is used to estimate altitude of the mobile device.
9 . The method of claim 7 , further comprising:
determining the estimate of the movement by the mobile device using an inertial sensor of the mobile device or using terrestrial or satellite ranging signals received by the mobile device from transmitters at known locations or a satellite system.
10 . The method of claim 7 , wherein:
the atmospheric condition sensor is a temperature sensor, a pressure sensor, a humidity sensor, or a gas sensor.
11 . The method of claim 7 , wherein:
the measured atmospheric condition is temperature, pressure, or air density.
12 . A method for determining an estimate of a currently unknown altitude of a mobile device wherein the method comprises:
determining a location of the mobile device using location information;
measuring a pressure value at the location of the mobile device using a pressure sensor of the mobile device;
measuring a localized amount of a gas in the air at the location of the mobile device using a gas-measuring sensor co-located with the mobile device;
detecting a first measured amount of the gas that exceeds a tolerated threshold amount of gas; and
in response to detecting the first measured amount of the gas, determining the estimate of the currently unknown altitude of the mobile device using a previously-determined estimate of a previously unknown altitude of the mobile device and an estimate of movement by the mobile device between the previously unknown altitude and the currently unknown altitude and without using the measured pressure value from the pressure sensor of the mobile device.
13 . The method of claim 12 , further comprising:
detecting a second measured amount of the gas that does not exceed the tolerated threshold amount of gas; and
in response to detecting the second measured amount of the gas, determining the estimate of the currently unknown altitude of the mobile device using the measured pressure value from the pressure sensor of the mobile device as an input to a known barometric formula that is used to estimate altitude of the mobile device.
14 . The method of claim 12 , wherein:
the gas is carbon dioxide (CO 2 ).
15 . The method of claim 12 , further comprising:
determining the estimate of the movement by the mobile device using an inertial sensor of the mobile device or using terrestrial or satellite ranging signals received by the mobile device from transmitters at known locations or a satellite system.