Abstract: A calculated current lapse rate is determined for a geographical area that includes a location of a mobile device. The calculated current lapse rate provides an estimated air temperature variation with respect to altitude variation for the location of the mobile device. An altitude of the mobile device is estimated. An uncertainty of the altitude of the mobile device is estimated based on a reference pressure and a reference temperature for a reference plane that is within the geographical area, a device pressure for the mobile device, and the calculated current lapse rate.

Abstract: Determining, broadcasting and using reference pressure data in a network of transmitters. Particular embodiments described herein include machines that select atmospheric data from weather stations within a transmitter network, use the selected atmospheric data to determine a reference atmospheric value, and transmit the reference atmospheric value from a transmitter to a mobile device for use in estimating an altitude of the mobile device. The atmospheric data may include any of reference pressures form the weather stations, measured temperatures from the weather stations, or reference temperatures from the weather stations. The reference atmospheric value may include a reference pressure value of a reference altitude, or a reference temperature value.

Abstract: Multiple calibration results for calibrating a barometric pressure sensor based on data received from a device containing the sensor are determined and stored in a table. The table is updated based on rules regarding a relationship between each calibration result and a current calibration value. The calibration results are weighted and combined to determine a combined calibration result. The calibration value for calibrating the sensor is selected from the calibration results, the combined calibration results, or the current calibration value based on a selection criteria.

Abstract: A wholistic activity context is used to determine whether to calibrate a barometric pressure sensor of a mobile device. A pair of activity transitions are determined from three activities of the mobile device. A time relationship and a position relationship between the activity transitions is determined. An opportunity to calibrate the barometric pressure sensor occurs between the activity transitions. A calibration of the barometric pressure sensor is performed in response to determining that the time relationship and the position relationship indicate that the wholistic activity context surrounding the opportunity to calibrate the barometric pressure sensor is conducive to calibration.

Abstract: Extending the spatial coverage of a reference pressure network. Particular embodiments described herein include machines that initially determine that an estimated position of a mobile device resides outside a coverage area of a network of reference pressure sensors. Reference-level pressures corresponding to reference pressure sensors of the network are determined using measurements of pressure from the network of reference pressure sensors. A pressure pattern for a region that includes the estimated position and an area not included in the coverage area of the network is determined using reference-level pressures that were not determined using measurements of pressure from the network of reference pressure sensors. The reference-level pressures corresponding to reference pressure sensors of the network and the pressure pattern are used to determine a reference-level pressure value for use in calibrating a pressure sensor of the mobile device or for use in estimating an altitude of the mobile device.

Abstract: Determining when an estimated altitude of a mobile device can be used for calibration or location determination. Particular systems and methods determine an area in which the mobile device is expected to reside, determine an altitude value of each section of a plurality of sections in the area, determine if the altitude values meet a threshold condition, and determine that the estimated altitude of the mobile device can be used for determining the position of the mobile device or for calibrating a pressure sensor of the mobile device when the altitude values meet the threshold condition.

Abstract: Estimating a difference in height between floors in a building for use in estimating a height or an altitude of one of the floors. A height difference is estimated between a first floor and a second floor based on outdoor temperatures of first and second time periods, an indoor temperature of the first or second time period, and first and second estimated differences in height between the first and second floors that is based on measurements of pressure from mobile devices when the mobile devices were on the first and second floors during the first and second time periods.

Abstract: Pressure-based estimation of a mobile device altitude or calibration of a pressure sensor involves machines that determine if a reference-level pressure value based on one or more measurements of pressure from a network of weather stations should or should not be used to calibrate a pressure sensor of a mobile device or to estimate an altitude of the mobile device. If reference-level pressure value should be used, the reference-level pressure value is used to calibrate a pressure sensor of a mobile device or to estimate an altitude of the mobile device. If the reference-level pressure value should not be used, a trend in pressure is determined, an estimated reference-level pressure value based on the trend is determined, and the estimated reference-level pressure value is used to calibrate a pressure sensor of a mobile device or to estimate an altitude of the mobile device.

Abstract: A method involves determining, at a mobile device or a service, an uncertainty in height above a reference altitude, an estimated 2D position of the mobile device, and an uncertainty in terrain height above the reference altitude using the estimated 2D position. An uncertainty in height above terrain, of the mobile device, is determined at the mobile device or a server using the uncertainty in height above the reference altitude and the uncertainty in terrain height above the reference altitude.

Abstract: Estimating a difference in height between two floors in a building for use in estimating a height or an altitude of one of the two floors. Particular embodiments estimate a height difference between a first floor and a second floor based on a first outdoor temperature of a first time period, a second outdoor temperature of a second time period, a third temperature that is based on an indoor temperature of the first time period or the second time period, a first estimated difference in height between the first and second floors that is based on measurements of pressure from mobile devices when those mobile devices were on the first and second floors during the first time period, and a second estimated difference in height between the first and second floors that is based on measurements of pressure from mobile devices when those mobile devices were on the first and second floors during the second time period.

Abstract: A method involves determining, at a mobile device or a service, an uncertainty in height above a reference altitude, an estimated 2D position of the mobile device, and an uncertainty in terrain height above the reference altitude using the estimated 2D position. An uncertainty in height above terrain, of the mobile device, is determined at the mobile device or a server using the uncertainty in height above the reference altitude and the uncertainty in terrain height above the reference altitude.

Abstract: Multiple calibration results for calibrating a barometric pressure sensor based on data received from a device containing the sensor are determined and stored in a table. The table is updated based on rules regarding a relationship between each calibration result and a current calibration value. The calibration results are weighted and combined to determine a combined calibration result. The calibration value for calibrating the sensor is selected from the calibration results, the combined calibration results, or the current calibration value based on a selection criteria.

Abstract: Extending the spatial coverage of a reference pressure network. Particular embodiments described herein include machines that initially determine that an estimated position of a mobile device resides outside a coverage area of a network of reference pressure sensors. Reference-level pressures corresponding to reference pressure sensors of the network are determined using measurements of pressure from the network of reference pressure sensors. A pressure pattern for a region that includes the estimated position and an area not included in the coverage area of the network is determined using reference-level pressures that were not determined using measurements of pressure from the network of reference pressure sensors. The reference-level pressures corresponding to reference pressure sensors of the network and the pressure pattern are used to determine a reference-level pressure value for use in calibrating a pressure sensor of the mobile device or for use in estimating an altitude of the mobile device.

Abstract: Multiple calibration results for calibrating a barometric pressure sensor based on data received from a device containing the sensor are determined and stored in a table. The table is updated based on rules regarding a relationship between each calibration result and a current calibration value. The calibration results are weighted and combined to determine a combined calibration result. The calibration value for calibrating the sensor is selected from the calibration results, the combined calibration results, or the current calibration value based on a selection criteria.

Abstract: Calibrating a pressure sensor of a mobile device incudes determining an absolute calibration value used to calibrate pressure measurements by a pressure sensor of a mobile device; determining a first revisit zone as a first location to which the mobile device repeatedly returns; determining first and second calibrations for first and second visits to the first revisit zone; determining a first relative calibration adjustment value based on a difference between the first and second calibrations; determining an adjusted absolute calibration value based on a sum of the absolute calibration value and the first relative calibration adjustment value; and estimating an altitude of the mobile device based on a pressure measurement by the pressure sensor and the adjusted absolute calibration value.

Abstract: Methods and machines involve detecting when a mobile device is in a first area and a second area at different times, collecting pressure data from the mobile device and reference sensor(s) to estimate altitudes of the mobile device within the first area and the second area, collecting terrain altitudes associated with the first area and the second area, and using a difference between the estimated altitudes and a difference between the terrain altitudes to determine a height of a floor. The estimated floor height may be used to calibrate a pressure sensor of a mobile device.

Abstract: Determining contexts of mobile devices. Particular embodiments described herein include machines that determine two estimated positions of a mobile device that respectively correspond to first and second locations at first and second times, acquire sets of terrain or structural information for first and second areas that respectively include the first and second estimated positions, use the acquired sets of information and the estimated positions to determine if the mobile device was near or within a structure at the first and second times, determine one or more values that are indicative of vertical movement by the mobile device during a period of time between the first time and the second time, compare the one or more values to one or more threshold conditions, and determine a context of the mobile device based on the comparison.