Systems and methods for calibrating unstable sensors

A method, comprising:

• determining a first estimated altitude of a mobile device without using any measurement from a pressure sensor of the mobile device;
• generating a second estimated altitude of the mobile device using a measurement from the pressure sensor;
• estimating a pressure sensor error of the pressure sensor using the first estimated altitude and the second estimated altitude;
• and
• using the pressure sensor error to determine a calibration value for adjusting one or more measurements from the pressure sensor;
• wherein the calibration value is determined by:
• identifying a pressure sensor calibration equation that includes calibration coefficient values previously determined in a calibration of the pressure sensor;
• identifying temperature measurements of the pressure sensor and corresponding sensor error measurements for the pressure sensor, wherein each temperature measurement of the identified temperature measurements was measured when the pressure sensor made a corresponding measurement of pressure that was used to determine a corresponding sensor error measurement of the identified sensor error measurements;
• determining calibration coefficient adjustment values by performing a polynomial fit using the identified temperature measurements and corresponding sensor error measurements;
• determining an adjusted pressure sensor calibration equation by using the calibration coefficient adjustment values to adjust the previously determined calibration coefficient values of the pressure sensor calibration equation;
• and
• determining the calibration value using the adjusted pressure sensor calibration equation.

A method, comprising:

• determining a first estimated altitude of a mobile device without using any measurement from a pressure sensor of the mobile device;
• generating a second estimated altitude of the mobile device using a measurement from the pressure sensor;
• estimating a pressure sensor error of the pressure sensor using the first estimated altitude and the second estimated altitude;
• and
• using the pressure sensor error to determine a calibration value for adjusting one or more measurements from the pressure sensor, comprising:
• retrieving one or more previously estimated sensor errors of the pressure sensor from storage;
• computing an average sensor error by averaging the estimated sensor error and the one or more previously estimated sensor errors;
• and
• using the average sensor error as the calibration value;
• wherein the pressure sensor error is estimated by:
• determining a difference in distance between the first estimated altitude and the second estimated altitude;
• determining an estimated difference in pressure between the first estimated altitude and the second estimated altitude based on the difference in distance;
• and
• setting the pressure sensor error to the estimated difference in pressure.

A method, comprising:

• determining a first estimated altitude of a mobile device without using any measurement from a pressure sensor of the mobile device;
• generating a second estimated altitude of the mobile device using a measurement from the pressure sensor;
• estimating a pressure sensor error of the pressure sensor using the first estimated altitude and the second estimated altitude;
• and
• using the pressure sensor error to determine a calibration value for adjusting one or more measurements from the pressure sensor;
• wherein determining the first estimated altitude further comprises:
• identifying that a battery of the mobile device is charging;
• in response to identifying that the battery of the mobile device is charging, identifying an altitude of a stored position, and the stored position was determined using a number of estimated positions that is greater than a threshold number of estimated positions;
• receiving the altitude of the stored position;
• and
• determining that the first estimated altitude is the altitude of the stored position.