Method for calculating the distance to a ground target from an aerial vehicle

• US 10,337,864 B2
• Filed: 02/17/2016
• Issued: 07/02/2019
• Est. Priority Date: 02/20/2015
• Status: Active Grant

• Current Assignee: Flir Unmanned Aerial Systems AS (Teledyne Technologies Incorporated)
• Original Assignee: Flir Unmanned Aerial Systems AS (Teledyne Technologies Incorporated)
• Inventors: Melby, Jorunn Helene, Syvertsen, Jorgen, Muren, Petter, Johansen, Tom-Ivar
• Primary Examiner(s): Liew, Alex Kok S
• Application Number:
  US15/552,195
• Publication Number:
  US 20180051986A1
• Time in Patent Office: 1,231 Days
• CPC Class Codes: B64C 39/024 of the remote controlled vehicle type, i.e. RPV
• CPC Class Codes: B64U 2201/10 autonomous, i.e. by navigating independently from ground or air stations, e.g. by using inertial navigation systems [INS]
• CPC Class Codes: G01C 11/06 by comparison of two or more pictures of the same area
• CPC Class Codes: G01C 5/005 altimeters for aircraft G01C5/02, G01C5/06 take precedence
• CPC Class Codes: G01S 11/12 using electromagnetic waves other than radio waves
• CPC Class Codes: G05D 1/042 specially adapted for aircraft
• CPC Class Codes: G05D 1/046 to counteract a perturbation, e.g. gust of wind
• CPC Class Codes: G06T 2207/10032 Satellite or aerial image; Remote sensing
• CPC Class Codes: G06T 7/579 from motion
• CPC Class Codes: G06T 7/70 Determining position or orientation of objects or cameras camera calibration G06T7/80
• CPC Class Codes: H04N 23/54 Mounting of pick-up tubes, electronic image sensors, deviation or focusing coils

Abstract

The present invention relates to a system and a method for measuring and determining the depth, offset and translation in relation to one or several features in the field of view of an image sensor equipped UAV. The UAV comprises at least an autopilot system capable of estimating rotation and translation, processing means, height measuring means and one or more imaging sensor means. Given the estimated translation provided by the autopilot system, the objective of the present invention is achieved by the following method; capturing an image, initiating a change in altitude, capturing a second image, comparing the images and the change in height provided by the sensor to produce a scale factor or depth. If depth is estimated, then calculating the scale factor from the depth, and calculating the actual translation with the resulting scale factor.

Claims

1. A method for determining a distance from an aerial vehicle to a target feature using an image sensor and an aviation altitude sensor each coupled to the aerial vehicle, the method comprising:

capturing, at a first position of the aerial vehicle, a first image including the target feature and a number of adjacent features;

receiving a first aviation altitude corresponding to the first position of the aerial vehicle;

altering a vertical position of the aerial vehicle from the first position to a second position of the aerial vehicle;

capturing, at the second position of the aerial vehicle, a second image including the target feature and the number of adjacent features;

receiving a second aviation altitude corresponding to the second position of the aerial vehicle; and

determining a target distance from the second position of the aerial vehicle to the target feature, wherein the target distance is based at least in part on the first aviation altitude, the second aviation altitude, a first pixel position of the target feature in the first image, and a second pixel position of the target feature in the second image.

2. The method of claim 1, wherein:

the image sensor is oriented substantially vertically; and

the target distance is related to the first aviation altitude, the second aviation altitude, a first pixel position of the target feature in the first image, and a second pixel position of the target feature in the second image by at least the following equation;

3. The method of claim 2, wherein:

the image sensor is oriented substantially vertically in the interval [335°

, 25°

] or [155°

, 205°

]; and

the image sensor is able to be oriented within a vertical plane such that 0°

is defined as the vertical downwards direction.

4. The method of claim 1, wherein:

the image sensor is oriented substantially between vertically and horizontally; and

the target distance is related to the first aviation altitude, the second aviation altitude, a first pixel position of the target feature in the first image, and a second pixel position of the target feature in the second image by at least the following equation;

5. The method of claim 4, wherein:

the image sensor is oriented substantially between vertically and horizontally in the interval [25°

, 65°

] or [115°

, 155°

] or [205°

, 245°

] or [295°

, 335°

]; and

0°

is defined as the vertical downwards direction.

6. The method of claim 1, wherein:

the image sensor is oriented substantially horizontally; and

the target distance is related to the first aviation altitude, the second aviation altitude, a first pixel position of the target feature in the first image, and a second pixel position of the target feature in the second image by at least the following equation;

7. The method of claim 6, wherein:

the image sensor is oriented substantially horizontally in the interval [65°

, 115°

] or [245°

, 295°

]; and

0°

is defined as the vertical downwards direction.

8. The method of claim 1, wherein:

the aviation altitude sensor comprises an air pressure sensor, an ultrasound sensor, a laser sensor, and/or a radar sensor configured to measure and provide aviation altitudes.

9. The method of claim 1, wherein the aviation altitude sensor comprises an air pressure sensor, the method further comprising:

determining an air pressure sensor offset corresponding to the air pressure sensor, wherein the air pressure sensor offset is related to the first aviation altitude, the second aviation altitude, a first pixel position of the target feature in the first image, and a second pixel position of the target feature in the second image by at least the following equation;

10. The method of claim 1, further comprising:

altering the vertical position of the aerial vehicle from the second position to the first position of the aerial vehicle;

capturing, at the first position of the aerial vehicle, a third image including at least the target feature;

receiving a third aviation altitude corresponding to the first position of the aerial vehicle; and

determining a second target distance from the first position of the aerial vehicle to the target feature, wherein the second target distance is based, at least in part, on the second aviation altitude, the third aviation altitude, the second pixel position of the target feature in the second image, and a third pixel position of the target feature in the third image.

11. A system comprising:

an autopilot for an aerial vehicle

an orientable image sensor configured to be coupled to the aerial vehicle; and

an aviation altitude sensor coupled to the aerial vehicle, wherein the autopilot is configured to;

capture, at a first position of the aerial vehicle, a first image including a target feature and a number of adjacent features;

receive a first aviation altitude corresponding to the first position of the aerial vehicle;

alter a vertical position of the aerial vehicle from the first position to a second position;

capture, at the second position of the aerial vehicle, a second image including the target feature and the number of adjacent features;

receive a second aviation altitude corresponding to the second position of the aerial vehicle; and

determine a target distance from the second position of the aerial vehicle to the target feature, wherein the target distance is based at least in part on the first aviation altitude, the second aviation altitude, a first pixel position of the target feature in the first image, and a second pixel position of the target feature in the second image.

12. The system of claim 11, wherein:

the image sensor is oriented substantially vertically; and

the target distance is related to the first aviation altitude, the second aviation altitude, a first pixel position of the target feature in the first image, and a second pixel position of the target feature in the second image by at least the following equation;

13. The system of claim 12, wherein:

the image sensor is oriented substantially vertically in the interval [335°

, 25°

] or [155°

, 205°

]; and

0°

is defined as the vertical downwards direction.

14. The system of claim 11, wherein:

the image sensor is oriented substantially between vertically and horizontally; and

the target distance is related to the first aviation altitude, the second aviation altitude, a first pixel position of the target feature in the first image, and a second pixel position of the target feature in the second image by at least the following equation;

15. The system of claim 14, wherein:

the image sensor is oriented substantially between vertically and horizontally in the interval [25°

, 65°

] or [115°

, 155°

] or [205°

, 245°

] or [295°

, 335°

]; and

0°

is defined as the vertical downwards direction.

16. The system of claim 11, wherein:

the image sensor is oriented substantially horizontally; and

the target distance is related to the first aviation altitude, the second aviation altitude, a first pixel position of the target feature in the first image, and a second pixel position of the target feature in the second image by at least the following equation;

17. The system of claim 16, wherein:

the image sensor is oriented substantially horizontally in the interval [65°

, 115°

] or [245°

, 295°

]; and

0°

is defined as the vertical downwards direction.

18. The system of claim 11, wherein:

the aviation altitude sensor comprises an air pressure sensor, an ultrasound sensor, a laser sensor, and/or a radar sensor configured to measure and provide aviation altitudes.

19. The system of claim 11, wherein the aviation altitude sensor comprises an air pressure sensor, and wherein the autopilot is configured to:

determine an air pressure sensor offset corresponding to the air pressure sensor, wherein the air pressure sensor offset is related to the first aviation altitude, the second aviation altitude, a first pixel position of the target feature in the first image, and a second pixel position of the target feature in the second image by at least the following equation;

20. The system of claim 11, wherein the autopilot is further configured to:

alter the vertical position of the aerial vehicle from the second position to the first position of the aerial vehicle;

capture, at the first position of the aerial vehicle, a third image including at least the target feature;

receive a third aviation altitude corresponding to the first position of the aerial vehicle; and

determine a second target distance from the first position of the aerial vehicle to the target feature, wherein the second target distance is based, at least in part, on the second aviation altitude, the third aviation altitude, the second pixel position of the target feature in the second image, and a third pixel position of the target feature in the third image.