Designing a calibration system for use in calibrating unstable sensors

Patent metadata

Field	Value
Publication number	US-10551271-B2
Application number	US-201615288274-A
Country	US
Kind code	B2
Filing date	Oct 7, 2016
Priority date	Oct 12, 2015
Publication date	Feb 4, 2020
Grant date	Feb 4, 2020

Abstract

Using a calibration sensor to calibrate an unstable sensor from a network of unstable sensors. Approaches for using a calibration sensor to calibrate the unstable sensor initially identify an unstable sensor in a geographic region to be calibrated by a calibration sensor using a model of environmental conditions for the geographic region, and then use the model to determine how to calibrate the unstable sensor using the calibration sensor.

First claim

The invention claimed is:

1. A method for using a calibration sensor to calibrate an unstable sensor, the method comprising:
identifying an unstable sensor in a geographic region to be calibrated by a calibration sensor,
wherein the identifying comprises identifying the unstable sensor, from among other unstable sensors, to be calibrated by the calibration sensor only when a distance separating the unstable sensor and the calibration sensor is less than a maximum distance,
wherein the maximum distance is a distance identified from a model of environmental conditions for the geographic region that corresponds to an amount of time equal to a maximum time over which an expected amount of drift by the unstable sensor will reach a maximum drift error based on an expected drift rate; and
calibrating the unstable sensor using the calibration sensor.

2. The method of claim 1 , wherein the calibrating comprises:
determining a time period during which an average of differences between pressure measurements from the calibration sensor and the unstable sensor is less than a pressure difference threshold;
setting a calibration period equal to or less than the maximum time over which the expected amount of drift by the unstable sensor will reach the maximum drift error;
during the calibration period, determining an additional average of differences between pressure measurements from the calibration sensor and the unstable sensor taken over the determined time period; and
calibrating the unstable sensor using the additional average of differences between pressure measurements from the calibration sensor and the unstable sensor taken over the determined time period during the calibration period.

3. The method of claim 2 , wherein determining a time period during which an average of differences between pressure measurements from the calibration sensor and the unstable sensor is less than a pressure difference threshold comprises:
identifying a first time period from a model of environmental conditions that is associated with a distance separating the unstable sensor and calibration sensor, and that is less than the maximum time over which the expected amount of drift by the unstable sensor will reach the maximum drift error;
determining, during the first time period, a first average of differences between pressure measurements from the calibration sensor and the unstable sensor;
determining if the first average is greater than the pressure difference threshold; and
if the first average is less than or equal to the pressure difference threshold, setting the time period to the first time period.

4. The method of claim 3 , wherein if the first average is greater than the pressure difference threshold, the method comprises:
identifying a second time period from the model of environmental conditions that is greater than the first time period and less than the maximum time over which the expected amount of drift by the unstable sensor will reach the maximum drift error;
determining, during the second time period, a second average of differences between pressure measurements from the calibration sensor and the unstable sensor;
determining if the second average is greater than the pressure difference threshold; and
if the second average is less than or equal to the pressure difference threshold, setting the time period to the second time period.

5. The method of claim 4 , wherein if the second average is greater than the pressure difference threshold, the method comprises:
identifying an additional time period;
determining if the additional time period is greater than the maximum time over which the expected amount of drift by the unstable sensor will reach the maximum drift error;
determining, if the additional time period is greater than the maximum time, whether the unstable sensor is a replacement sensor;
generating, if the unstable sensor is not a replacement sensor, data specifying that the unstable sensor is to be replaced; and
generating, if the unstable sensor is a replacement sensor, data specifying that the unstable sensor is to be calibrated by another calibration sensor.

6. The method of claim 3 , wherein if the first average is greater than the pressure difference threshold, the method comprises:
identifying an additional time period;
determining if the additional time period is greater than the maximum time over which the expected amount of drift by the unstable sensor will reach the maximum drift error;
determining, if the additional time period is greater than the maximum time, whether the unstable sensor is a replacement sensor;
generating, if the unstable sensor is not a replacement sensor, data specifying that the unstable sensor is to be replaced; and
generating, if the unstable sensor is a replacement sensor, data specifying that the unstable sensor is to be calibrated by another calibration sensor.

7. The method of claim 1 , wherein the model of environmental conditions specifies different combinations of distances and times, wherein each time for each combination of distance and time represents an amount of time needed for an average of differences in pressure measured at locations separated by the distance of the combination to be below a pressure difference threshold.

8. The method of claim 1 , wherein the model of environmental conditions specifies, for each of a plurality of different distances, a time period over which an average difference in measured pressures from two locations in the geographic region that are separated by that distance is less than or equal to a maximum difference.

9. The method of claim 8 , wherein the model of environmental conditions is determined by:
averaging, over different time periods, differences between pressure measurements at two locations in the geographic region that are separated by a first distance; and
averaging, over the different time periods, differences between pressure measurements at two locations in the geographic region that are separated by a second distance.

10. The method of claim 1 , wherein the maximum drift error is 10 Pascals.

11. A method for using a calibration sensor to calibrate an unstable sensor, wherein the method comprises:
identifying an unstable sensor in a geographic region to be calibrated by a calibration sensor; and
calibrating the unstable sensor using the calibration sensor, wherein the calibrating comprises:
(i) determining a time period during which an average of differences between pressure measurements from the calibration sensor and the unstable sensor is less than a pressure difference threshold;
(ii) setting a calibration period equal to or less than a maximum time over which an expected amount of drift by the unstable sensor will reach a maximum drift error;
(iii) during the calibration period, determining an additional average of differences between pressure measurements from the calibration sensor and the unstable sensor taken over the determined time period; and
(iv) calibrating the unstable sensor using the additional average of differences between pressure measurements from the calibration sensor and the unstable sensor taken over the determined time period during the calibration period.

12. The method of claim 11 , wherein calibrating the unstable sensor using the additional average of differences comprises: adjusting a measurement from the unstable sensor by the additional average of differences.

13. The method of claim 11 , wherein determining a time period during which an average of differences between pressure measurements from the calibration sensor and the unstable sensor is less than a pressure difference threshold comp

Assignees

• Nextnav Llc

Inventors

• Dormody Michael
• Wolf Thomas

Classifications

• G01C25/00

  Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass (testing, calibrating or compensating compasses G01C17/38) · CPC title

• G01D18/00

  Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00 · CPC title

• G01L27/005 Primary

  Apparatus for calibrating pressure sensors · CPC title

• G01C5/06 Primary

  by using barometric means · CPC title