Low-light and no-light aerial navigation

1. An unmanned aerial vehicle (UAV) comprising:

a global navigation satellite system (GNSS) receiver;

an inertial measurement unit having an associated accelerometer and gyroscope; and

one or more processors configured by executable instruction to perform operations comprising:

receiving location information via the GNSS receiver;

determining first accelerations of the UAV in a navigation frame of reference based on information from the accelerometer and the gyroscope received prior to or during takeoff;

determining second accelerations of the UAV in a world frame of reference based on the location information received via the GNSS receiver prior to or during takeoff;

determining a plurality of relative headings of the UAV respectively based on the first accelerations and the second accelerations;

selecting one of the plurality of relative headings based on a largest subset of the plurality of relative headings matching each other within a threshold amount; and

performing navigation of the UAV at least one of during or after takeoff of the UAV based on the selected relative heading.

2. The UAV as recited in claim 1 , the operations further comprising:

establishing a plurality of bins, each bin corresponding to a range of heading angles;

matching individual relative headings to individual ones of the bins based on matching the heading angle with a bin range;

assigning one or more points to a respective bin based on a match between a heading angle and the respective bin; and

selecting one of the bins as indicating the heading angle for the selected relative heading when the number of points assigned to the bin exceeds a points threshold.

3. The UAV as recited in claim 2 , the operations further comprising increasing an amount of points or a weighting of points assigned to the respective bin based on a magnitude of a corresponding first acceleration or second acceleration for a respective heading angle.

4. The UAV as recited in claim 1 , wherein the threshold amount is a first threshold amount, the operations further comprising:

determining a confidence value for the selected relative heading based at least on a number of matches within a second threshold amount of the largest subset of the relative headings matching each other within the first threshold amount; and

selecting the selected relative heading based in part on the confidence value being above a threshold confidence value.

5. The UAV as recited in claim 1 , the operations further comprising:

receiving the first accelerations and the second accelerations prior to takeoff of the UAV based on motion induced on the UAV prior to takeoff.

6. The UAV as recited in claim 1 , the operations further comprising:

receiving the first accelerations and the second accelerations during takeoff of the UAV by causing the UAV to takeoff using a known acceleration profile.

7. A method comprising:

inducing motion on an unmanned aerial vehicle (UAV) prior to takeoff;

determining, by one or more processors, first accelerations of the UAV based on information from an accelerometer onboard the UAV;

determining second accelerations of the UAV based on location information received via a global navigation satellite system (GNSS) receiver;

determining a plurality of relative headings of the UAV respectively based on the first accelerations and the second accelerations;

selecting one of the plurality of relative headings based on a largest subset of the plurality of relative headings matching each other within a threshold amount; and

performing navigation of the UAV at least one of during or after takeoff of the UAV based on the selected relative heading.

8. The method as recited in claim 7 , further comprising inducing the motion on the UAV by moving the UAV in a back-and-forth motion prior to takeoff.

9. The method as recited in claim 7 , determining the first accelerations in a navigation frame of reference based on an output from an inertial measurement unit (IMU) that is associated with the accelerometer.

10. The method as recited in claim 7 , further comprising determining the second accelerations in a world frame of reference based on the location information received via the GNSS receiver by determining finite differences in velocity signals determined based on the received location information.

11. The method as recited in claim 7 , further comprising:

establishing a plurality of bins, each bin corresponding to a range of heading angles;

matching individual relative headings to individual ones of the bins based on matching the heading angle with a bin range;

assigning one or more points to a respective bin based on a match between a heading angle and the respective bin; and

selecting one of the bins as indicating the heading angle for the selected relative heading when the number of points assigned to the bin exceeds a points threshold.

12. The method as recited in claim 7 , wherein the threshold amount is a first threshold amount, the method further comprising:

determining a confidence value for the selected relative heading based at least on a number of matches within a second threshold amount of the largest subset of the relative headings matching each other within a first threshold amount; and

selecting the relative heading based in part on the confidence value being above a threshold confidence value.

13. A method comprising:

configuring an unmanned aerial vehicle (UAV) to takeoff at a specified trajectory using a specified acceleration profile;

determining, by one or more processors of the UAV, first accelerations of the UAV based on information from an accelerometer onboard the UAV during takeoff;

determining second accelerations of the UAV based on location information received via a global navigation satellite system (GNSS) receiver during the takeoff;

determining a plurality of relative headings of the UAV respectively based on the first accelerations and the second accelerations;

selecting one of the plurality of relative headings based on a largest subset of the plurality of relative headings matching each other within a threshold amount; and

performing navigation of the UAV after takeoff of the UAV based on the selected relative heading.

14. The method as recited in claim 13 , wherein the specified trajectory is diagonal to a ground plane.

15. The method as recited in claim 13 , determining the first accelerations in a navigation frame of reference based on output from an inertial measurement unit (IMU) that is associated with the accelerometer.

16. The method as recited in claim 13 , further comprising determining the second accelerations in a world frame of reference based on the location information received via the GNSS receiver by determining finite differences in velocity signals determined based on the received location information.

17. The method as recited in claim 13 , further comprising:

establishing a plurality of bins, each bin corresponding to a range of heading angles;

matching individual relative headings to individual ones of the bins based on matching the heading angle with a bin range;

assigning one or more points to a respective bin based on a match between a heading angle and the respective bin; and

selecting one of the bins as indicating the heading angle for the selected relative heading when the number of points assigned to the bin exceeds a points threshold.