Device based barometric pressure sensor calibration
Device-based barometric pressure sensor calibration involves determining a specific location of the mobile device; determining a general location of the mobile device that encompasses and obfuscates the specific location; transmitting the general location to a server; receiving general calibration data for the general location; determining specific calibration data based on the general calibration data and the specific location; determining a calibration value based on the specific calibration data, the calibration value being for calibrating the barometric pressure sensor.
1. A method comprising:
determining, by a mobile device, a specific location and a specific location area of the mobile device, wherein the specific location is based on position data from a position sensor of the mobile device and the specific location area is based on a confidence interval value associated with the position data;
determining, by the mobile device, a general location of the mobile device that encompasses and obfuscates the specific location, wherein the specific location is obfuscated by the general location not revealing the specific location, and the general location comprises a bounding area that encompasses and is larger than the specific location area;
transmitting, by the mobile device, the general location to a server;
receiving, by the mobile device from the server, general calibration data for the general location;
determining, by the mobile device, specific calibration data based on the general calibration data and the specific location;
determining, by the mobile device, a device pressure based on a pressure measurement by a barometric pressure sensor of the mobile device;
determining, by the mobile device, a calibration value based on the specific calibration data and the device pressure, the calibration value being for calibrating the barometric pressure sensor; and
calculating, by the mobile device, an altitude of the mobile device using the calibration value and a subsequent pressure measurement by the barometric pressure sensor.
2. The method of claim 1 , wherein:
the specific location is at any point within the bounding area.
3. The method of claim 1 , wherein receiving the general calibration data further comprises:
receiving terrain and building data with respect to the bounding area; and
receiving reference pressure data and reference temperature data for a region that encompasses the bounding area, the reference pressure data and the reference temperature data being based on pressure measurements and temperature measurements generated by reference weather stations.
4. The method of claim 3 , wherein determining the specific calibration data further comprises:
determining specific terrain and building data for the specific location from the terrain and building data;
determining a possible altitude for the mobile device based on the specific terrain and building data; and
determining a specific reference pressure and a specific reference temperature for the specific location from the reference pressure data and the reference temperature data for the region that encompasses the bounding area.
5. The method of claim 3 , wherein:
the terrain and building data comprises a portion of a terrain and building database.
6. The method of claim 3 , wherein:
the terrain and building data comprises a terrain and building distribution for a latitude and longitude confidence surrounding the bounding area.
7. The method of claim 3 , wherein:
the terrain and building data comprises a polynomial model that has been fit to data of a terrain and building database.
8. The method of claim 3 , wherein:
the reference pressure data and reference temperature data comprises data of a reference pressure and temperature database.
9. The method of claim 3 , wherein:
the reference pressure data and reference temperature data comprises a polynomial model that has been fit to data of a reference pressure and temperature database.
10. The method of claim 3 , further comprising:
storing, by the mobile device, the terrain and building data, the reference pressure data, and the reference temperature data; and
upon determining that the mobile device is not within the bounding area, deleting, by the mobile device, the terrain and building data, the reference pressure data, and the reference temperature data.
11. The method of claim 3 , wherein:
the terrain and building data includes terrain quality data with respect to the bounding area.
12. The method of claim 1 , wherein:
a size of the bounding area depends on a level of a privacy requirement for the mobile device, such that a larger bounding area is selected for a higher privacy requirement and a smaller bounding area is selected for a lower privacy requirement.
13. A method comprising:
determining, by a mobile device, a specific location of the mobile device, wherein the specific location is based on position data from a position sensor of the mobile device;
determining, by the mobile device, a general location of the mobile device that encompasses and obfuscates the specific location;
transmitting, by the mobile device, the general location to a server;
receiving, by the mobile device from the server, general calibration data for the general location;
determining, by the mobile device, specific calibration data based on the general calibration data and the specific location;
determining, by the mobile device, a device pressure based on a pressure measurement by a barometric pressure sensor of the mobile device;
determining, by the mobile device, a calibration value based on the specific calibration data and the device pressure, the calibration value being for calibrating the barometric pressure sensor; and
calculating, by the mobile device, an altitude of the mobile device using the calibration value and a subsequent pressure measurement by the barometric pressure sensor;
wherein:
the general location comprises a plurality of locations which includes the specific location and a remainder of locations;
the plurality of locations is within a region;
the specific location is at any point within the region; and
the general location obfuscates the specific location by the specific location being at any point within the region.
14. The method of claim 13 , wherein receiving the general calibration data further comprises:
receiving a possible altitude for each location of the plurality of locations; and
receiving a reference pressure and a reference temperature for each location of the plurality of locations.
15. The method of claim 14 , wherein determining the specific calibration data further comprises:
determining a specific possible altitude for the mobile device by selecting the received possible altitude for the specific location; and
determining a specific reference pressure and a specific reference temperature for the specific location by selecting the received reference pressure and the received reference temperature for the specific location.
16. The method of claim 14 , wherein receiving the general calibration data further comprises:
receiving terrain quality data for each location of the plurality of locations.
17. The method of claim 13 , wherein:
the plurality of locations is selected to be arranged in a grid pattern within the region.
18. The method of claim 13 , wherein:
the plurality of locations is selected to be at random latitude and longitude points within the region.
19. The method of claim 13 , wherein:
a size of the region depends on a level of a privacy requirement for the mobile device, such that a larger region is selected for a higher privacy requirement and a smaller region is selected for a lower privacy requirement.
20. The method of claim 13 , wherein:
a number of the remainder of locations depends on a level of a privacy requirement for the mobile device, such that a larger number is selected for a higher privacy requirement and a smaller number is selected for a lower privacy requirement.