UAV Canopy Height Determination Using Stabilized Optical Imaging
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Solution Overview
Problem
Current methods for determining the flight height of unmanned aerial vehicles (UAVs) over agricultural and forestry crops are inaccurate due to interference from canopy density, soil moisture, air humidity, and solar radiation, leading to unstable relative height measurements and blurred images.
Innovation Solution
A device and system comprising a three-axis self-stabilizing tripod head, carrier phase difference satellite positioning system, attitude and heading reference system, and a graphics processing computer, which uses high-resolution visible light cameras to calculate the relative height between the UAV and crop canopy, ensuring stable flight height determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser rangefinder or ultrasonic rangefinder is used to measure relative height by averaging several points, then measurement can be performed, but the relative height between UAV and crop canopy cannot be monitored stably due to interference from canopy density, soil moisture, air humidity and solar radiation
Solution Approach 1:
The patent replaces mechanical/radar-based rangefinding systems with an optical imaging system (camera) combined with photogrammetric processing. Instead of using laser or ultrasonic waves that are affected by atmospheric conditions, the system uses visible light imaging and geometric processing to determine height, substituting a physical measurement field with another that is less sensitive to the mentioned interferences.
Solution Approach 2:
The patent introduces an intermediary processing system (graphics processing computer with photogrammetric algorithms) that mediates between the raw image data and the final height measurement. This intermediary processes multiple image points and uses geometric relationships to calculate height, filtering out the direct effects of canopy density, moisture, humidity and radiation that would otherwise directly affect simple rangefinding.
2Ease of operation
If UAV flies at fixed altitude in plain areas, then operation is simple, but in terraced fields or hilly areas the UAV cannot adapt to terrain variations and maintain proper imaging distance
Solution Approach 1:
The patent transforms the static fixed-altitude flight mode into a dynamic terrain-following mode. The system continuously processes image data to calculate relative height and provides real-time feedback for altitude adjustment, allowing the UAV to dynamically adapt its flight path to match terrain contours in terraced fields and hilly areas while maintaining optimal imaging distance.
Solution Approach 2:
The patent implements a feedback control loop where the graphics processing computer continuously analyzes image data to determine relative height, compares it with desired imaging parameters, and provides feedback for altitude adjustment. This closed-loop system enables automatic adaptation to terrain variations without requiring manual intervention.
3Device complexity
If common airborne devices use averaging method to calculate relative height, then calculation is simple, but the accuracy is insufficient and data stability is poor
Solution Approach 1:
The patent divides the imaging area into multiple discrete measurement points rather than relying on a single averaged value. By processing multiple individual image features and their corresponding ground positions, the system obtains a distribution of height measurements that can be analyzed for both accuracy and consistency, replacing the simple averaging approach with a multi-point geometric analysis.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate and stable monitoring of the UAV's flight height relative to crop canopies, improving data acquisition accuracy and image clarity by objectively controlling altitude based on terrain, thereby enhancing information gathering and data stability.
Implementation Method 1
a carrier phase difference satellite positioning system
Implementation Method 2
a three-axis self-stabilizing tripod head, and the three-axis self-stabilizing tripod head is used to maintain the optical axis of the camera
Implementation Method 3
an attitude and heading reference system
Data Source
AI summary
A method and system for determining flight height of an unmanned aerial vehicle (UAV) includes a determining device that includes a camera at bottom of the UAV carried on a three-axis self-stabilizing tripod head; and a carrier phase difference satellite positioning system (CPDSPS), a graphics processing computer (GPC) and a power supply system provided on top of the UAV The GPC is connected with the CPDSPS, the power supply system and the camera, respectively. An attitude and heading reference system (AHRS) is provided at the bottom of the three-axis self-stabilizing tripod head and connected with the GPC The GPC is configured to determine relative height of the UAV from a canopy of farmland surface crops according to position information acquired by the CPDSPS, attitude information acquired by the AHRS and ground orthographic image acquired by the camera, and determine flight height of the UAV according to the relative height.