To reduce the number of false detections when using the virtual loop feature in a fixed SharpV installation, you must consider the guidelines for drawing the detection zone.
Virtual loop detection zone guidelines:
- The polygon must touch the border of the image. This is necessary for all direction of travel settings, for example, Enters the field of view in the detection zone.
- The detection zone should be close to the camera.
- The polygon lines cannot intersect.
- To be detected, at least 25% of the visible part of the vehicle must pass through the red detection zone (if configured) when the vehicle enters or exits the image. The vehicle must also cover at least 20% of the orange ALPR field of view somewhere along its trajectory.
- Try to draw your detection zone so that cyclists and pedestrians do not pass through the zone. For example, if you have too many false detections when you draw a polygon far from the camera and use the Exits the field of view in the detection zone setting, try drawing a polygon close to the camera and use the Enters the field of view in the detection zone setting.
Issue: The detection zone does not touch the edge of the field of view
- Bad
- The detection zone polygon (drawn in red) covers the parking lot entrance, but it does not touch the edge of the context camera field of view. With this detection zone, no vehicles are detected.
- Good
- The detection zone touches the edge of the context camera field of view. To detect only vehicles exiting the parking lot, use the Enters the field of view in the detection zone setting.
Issue: Vehicles do not leave the field of view
- Bad
- To be detected, vehicles must exit the context camera field of view. Some of the parking spaces in this parking lot are within the detection zone. As a result, the vehicles in those spaces are not detected. Also, the detection zone is too far from the camera.
- Good
- To correct this issue, the camera angle has been lowered (which requires zoom and
focus recalibration) and the Enters the field of view in the detection zone
setting is used. Also, the detection zone is now closer to the
camera.
Alternatively, you could reduce the size of the context camera's field of view so that the vehicles in the parking lot are not visible.
Issue: 25% of the vehicle is not within the detection zone
- Bad
- To be detected, at least 25% of the visible part of the vehicle must pass through the red detection zone. In this example, the detection zone is drawn to match the road. Especially when the camera is installed close to the ground, this can mean that vehicles are excluded.