Systems and methods for determining calibration values for atmospheric sensors that provide measured pressures used for estimating altitudes of mobile devices

1. A method for determining calibration values for atmospheric sensors that provide measured pressures used for estimating altitudes of mobile devices, the method comprising:

for different periods of time, determining an uncalibrated reference-level pressure estimate associated with an unstable pressure sensor and a calibrated reference-level pressure estimate associated with a stable pressure sensor;

determining if the uncalibrated reference-level pressure estimates include any uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor;

if the uncalibrated reference-level pressure estimates do not include any uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor, determining a calibration value for the unstable pressure sensor using all of the uncalibrated reference-level pressure estimates; and

if the uncalibrated reference-level pressure estimates include an uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor:

identifying at least one uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor; and

determining a calibration value for the unstable pressure sensor using all of the uncalibrated reference-level pressure estimates except any identified uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor.

2. The method of claim 1 , wherein determining if the uncalibrated reference-level pressure estimates include any uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor comprises:

determining an initial calibration value using the uncalibrated reference-level pressure estimates and the calibrated reference-level pressure estimate;

for each of the periods of time, determining an adjusted reference-level pressure estimate for the period of time by adjusting the uncalibrated reference-level pressure estimate for the period of time by the initial calibration value;

for each of the periods of time, determining a difference between (i) the adjusted reference-level pressure estimate for the period of time and (ii) the calibrated reference-level pressure estimate for the period of time;

determining if a threshold amount of the determined differences are less than a threshold pressure difference;

if each determined difference in the threshold amount of the determined differences is less than the threshold pressure difference, determining that the uncalibrated reference-level pressure estimates do not include any uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor; and

if each determined difference in the threshold amount of the determined differences is not less than the threshold pressure difference, determining that the uncalibrated reference-level pressure estimates include an uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor.

3. The method of claim 1 , wherein determining if the uncalibrated reference-level pressure estimates include any uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor comprises:

for each of the periods of time, determining a difference between (i) the uncalibrated reference-level pressure estimate for the period of time and (ii) the calibrated reference-level pressure estimate for the period of time;

determining a mean or median of the differences;

determining if a threshold amount of the determined differences are within a threshold pressure difference from the mean or median of the differences;

if each determined difference in the threshold amount of the determined differences is within the threshold pressure difference from the mean or median of the differences, determining that the uncalibrated reference-level pressure estimates do not include any uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor; and

if each determined difference in the threshold amount of the determined differences is not within the threshold pressure difference from the mean or median of the differences, determining that the uncalibrated reference-level pressure estimates include an uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor.

4. The method of claim 1 , wherein identifying at least one uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor comprises:

for each of the periods of time, determining a difference between (a) the uncalibrated reference-level pressure estimate of the time period and (b) the calibrated reference-level pressure estimate for the period of time;

for each of the periods of time, determining if the determined difference for the period of time meets a threshold condition;

if the determined difference for the period of time meets the threshold condition, identifying the uncalibrated reference-level pressure estimate as one of the uncalibrated reference-level pressure estimates that should not be used when calibrating the unstable pressure sensor; and

if the determined difference for the period of time does not meet the threshold condition, not identifying the uncalibrated reference-level pressure estimate as one of the uncalibrated reference-level pressure estimates that should not be used when calibrating the unstable pressure sensor.

5. The method of claim 1 , wherein identifying at least one uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor comprises:

determining an initial calibration value using the uncalibrated reference-level pressure estimates and the calibrated reference-level pressure estimates;

for each of the periods of time, determining an adjusted reference-level pressure estimate for the period of time by adjusting the uncalibrated reference-level pressure estimate for the period of time by the initial calibration value;

for each of the periods of time, determining a difference between (a) the adjusted reference-level pressure estimate of the time period and (b) the calibrated reference-level pressure estimate for the period of time;

for each of the periods of time, determining if the determined difference for the period of time meets a threshold condition;

if the determined difference for the period of time meets the threshold condition, identifying the uncalibrated reference-level pressure estimate as one of the uncalibrated reference-level pressure estimates that should not be used when calibrating the unstable pressure sensor; and

if the determined difference for the period of time does not meet the threshold condition, not identifying the uncalibrated reference-level pressure estimate as one of the uncalibrated reference-level pressure estimates that should not be used when calibrating the unstable pressure sensor.

6. A system for determining calibration values for atmospheric sensors that provide measured pressures used for estimating altitudes of mobile device, the system comprising one or more machines configured to perform the method of claim 1 .

7. One or more non-transitory machine-readable media embodying program instructions that, when executed by one or more machines, cause the one or more machines to implement a method for determining calibration values for atmospheric sensors that provide measured pressures used for estimating altitudes of mobile devices, the method comprising:

for different periods of time, determining an uncalibrated reference-level pressure estimate associated with an unstable pressure sensor and a calibrated reference-level pressure estimate associated with a stable pressure sensor;

determining if the uncalibrated reference-level pressure estimates include any uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor;

if the uncalibrated reference-level pressure estimates do not include any uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor, determining a calibration value for the unstable pressure sensor using all of the uncalibrated reference-level pressure estimates; and

if the uncalibrated reference-level pressure estimates include an uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor:

identifying at least one uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor; and

determining a calibration value for the unstable pressure sensor using all of the uncalibrated reference-level pressure estimates except any identified uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor.

8. The one or more non-transitory machine-readable media claim 7 , wherein determining if the uncalibrated reference-level pressure estimates include any uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor comprises:

determining an initial calibration value using the uncalibrated reference-level pressure estimates and the calibrated reference-level pressure estimate;

for each of the periods of time, determining an adjusted reference-level pressure estimate for the period of time by adjusting the uncalibrated reference-level pressure estimate for the period of time by the initial calibration value;

for each of the periods of time, determining a difference between (i) the adjusted reference-level pressure estimate for the period of time and (ii) the calibrated reference-level pressure estimate for the period of time;

determining if a threshold amount of the determined differences are less than a threshold pressure difference;

if each determined difference in the threshold amount of the determined differences is less than the threshold pressure difference, determining that the uncalibrated reference-level pressure estimates do not include any uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor; and

if each determined difference in the threshold amount of the determined differences is not less than the threshold pressure difference, determining that the uncalibrated reference-level pressure estimates include an uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor.

9. The one or more non-transitory machine-readable media claim 7 , wherein determining if the uncalibrated reference-level pressure estimates include any uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor comprises:

for each of the periods of time, determining a difference between (i) the uncalibrated reference-level pressure estimate for the period of time and (ii) the calibrated reference-level pressure estimate for the period of time;

determining a mean or median of the differences;

determining if a threshold amount of the determined differences are within a threshold pressure difference from the mean or median of the differences;

if each determined difference in the threshold amount of the determined differences is within the threshold pressure difference from the mean or median of the differences, determining that the uncalibrated reference-level pressure estimates do not include any uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor; and

if each determined difference in the threshold amount of the determined differences is not within the threshold pressure difference from the mean or median of the differences, determining that the uncalibrated reference-level pressure estimates include an uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor.

10. The one or more non-transitory machine-readable media claim 7 , wherein identifying at least one uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor comprises:

for each of the periods of time, determining a difference between (a) the uncalibrated reference-level pressure estimate of the time period and (b) the calibrated reference-level pressure estimate for the period of time;

for each of the periods of time, determining if the determined difference for the period of time meets a threshold condition;

if the determined difference for the period of time meets the threshold condition, identifying the uncalibrated reference-level pressure estimate as one of the uncalibrated reference-level pressure estimates that should not be used when calibrating the unstable pressure sensor; and

if the determined difference for the period of time does not meet the threshold condition, not identifying the uncalibrated reference-level pressure estimate as one of the uncalibrated reference-level pressure estimates that should not be used when calibrating the unstable pressure sensor.

11. The one or more non-transitory machine-readable media claim 7 , wherein identifying at least one uncalibrated reference-level pressure estimate that should not be used when calibrating the unstable pressure sensor comprises:

determining an initial calibration value using the uncalibrated reference-level pressure estimates and the calibrated reference-level pressure estimates;

for each of the periods of time, determining an adjusted reference-level pressure estimate for the period of time by adjusting the uncalibrated reference-level pressure estimate for the period of time by the initial calibration value;

for each of the periods of time, determining a difference between (a) the adjusted reference-level pressure estimate of the time period and (b) the calibrated reference-level pressure estimate for the period of time;

for each of the periods of time, determining if the determined difference for the period of time meets a threshold condition;

if the determined difference for the period of time meets the threshold condition, identifying the uncalibrated reference-level pressure estimate as one of the uncalibrated reference-level pressure estimates that should not be used when calibrating the unstable pressure sensor; and

if the determined difference for the period of time does not meet the threshold condition, not identifying the uncalibrated reference-level pressure estimate as one of the uncalibrated reference-level pressure estimates that should not be used when calibrating the unstable pressure sensor.