1. Provide real-time imagery from a designated border using drones
- Multiple quadcopters will remain in stationary observation positions along a designated border around the beach area (example below from Byron Bay in Australia) providing real-time images which will be sent to computer systems using radio or cellular networks.
2. Analysis of imagery using low-level feature extraction to detect shark-like shapes
- The images will subsequently be analysed by computers, and low-level feature extraction such as edge-detection can be performed
- Edge detection: what is an edge and how do we detect it?
Edge detection makes use of image contrast. Contrast (a difference in intensity) can emphasize the boundaries of an image (the edges) as this is where image contrast occurs. The boundary of an object is a step change in intensity level, the edge being at the position of the step change.
- The Canny Edge Detector is an edge-detection operator that could be used.
1. Use Gaussian smoothing
2. Use the Sobel operator for edge detection
3. Use nonmaximal suppression
4.Threshold with hysteresis to connect edge points
- Below we can see Sobel operator applied to a shark seen from the air
- Below we can see Canny Edge Detector applied to a photograph
3. Recharging and swapping of drones to provide continuous surveillance of the border
- After its batteries are nearly discharged, drone A will be replaced by drone B; drone A will then return to the beach and have its batteries swapped by lifeguards, before returning to replace drone B. It would be hoped that custom-built quadcopter drones can manage 1hr flight times (e.g. see below)
4. If sharks are detected, imagery can be verified by lifeguards before they act to remove swimmers and surfers from the water, and close the beach
Initial problems identified:
- 1. High cost of the number of drones required to monitor border
- 2. Beach users may object to the continuous presence of -- perhaps 100s of -- drones on the horizon!
- 3. Low battery life means drones can only hover for 1hr maximum - and that is using a custom-built drone! Commercially available drones may only manage 20 minutes!
- The low-battery life and the large number of drones required is certainly problematic! Thus, an alternative approach I have envisaged is the use of tethered balloons which can be maintained statically whilst carrying a payload containing high-resolution cameras. The balloons can be tethered on the beach or from platforms in the sea.