2. Camera Viewing Angles
Set camera tilt angle to 20–30° down, pan angle recommended 15° parallel to roadway, roll < +/-5° from horizon; choose proper FOV for accurate object detection.
Correctly configuring the Xvision camera viewing angles is essential for capturing high-quality images that enable accurate vehicle detection and monitoring. This section provides guidance on selecting the optimal vertical, horizontal and roll angles, as well as determining the appropriate field of view (FOV) for your detection cameras.
Summary of Key Points
Vertical Angle (Tilt Angle):
Set between 20° and 30° downward for optimal vehicle visibility and reduced occlusion.
Use tools and adjustable mounts for precise alignment.
Horizontal Angle (Pan Angle):
Position cameras perpendicular (90°) to traffic flow for consistent image capture and minimised motion blur.
Adjust for license plate recognition or site constraints as necessary, with corresponding system recalibration.
Horizontal Tilt to Horizon (Roll Angle):
Optimal Horizontal Tilt (Roll Angle): Keep the camera level, with less than +/-5° deviation from the true horizontal plane.
Field of View (FOV):
Choose appropriate lenses to balance coverage area and image detail.
Calculate FOV using camera specifications and adjust to cover all required detection zones without distortion.
Vertical Angle (Tilt Angle)
Optimal Tilt Angle: 20° to 30° downward from the horizontal plane.
Importance of the Vertical Angle
The vertical angle, or tilt angle, refers to how much the camera is angled downward relative to the horizontal plane. Setting this angle within the recommended range offers several benefits:
Benefits:
Enhanced Object Recognition:
Improved Visibility of Vehicle Surfaces:
Angling the camera downward captures both the top and sides of vehicles, providing a more comprehensive view.
This vantage point enhances the ability to identify vehicle types, makes, and models accurately.
Better Depth Perception:
A downward angle improves the three-dimensional appearance of vehicles in the footage.
Enhanced depth perception assists video analytics software in distinguishing between objects at varying distances.
Reduced Occlusion:
Minimised Vehicle Overlapping:
Proper tilt angle reduces the likelihood of one vehicle blocking another in the camera's view.
This is crucial in multi-lane monitoring where vehicles may pass each other.
Effective Multi-Lane Detection:
Ensures that all lanes are within the camera's field of view without significant blind spots.
Facilitates consistent detection across the entire monitored area.
Adjustment Tips:
Use of Tools:
Inclinometer or Digital Angle Finder:
Utilise these devices during installation to set the precise tilt angle.
Ensures accuracy and reduces the need for future adjustments.
Adjustable Mounts:
Consider mounts that allow for easy angle adjustments.
Provides flexibility during initial setup and for fine-tuning based on performance.
Testing at Different Times:
Day and Night Evaluations:
Test camera angles during various times of the day to account for changing light conditions.
Helps identify and mitigate issues like glare or shadows that can affect image quality.
Seasonal Considerations:
Be aware of how seasonal changes in sun position may impact the camera's performance.
Horizontal Angle (Pan Angle)
Recommended Pan Angle: Parallel (0-15°) to the direction of traffic flow.
Significance of the Horizontal Angle
The horizontal angle, or pan angle, determines the camera's side-to-side orientation relative to the traffic flow. Setting this angle correctly is vital for capturing consistent and clear images of moving vehicles.
Maximum Deviation Limit:
Angle Constraints:
Deviating more than 25° from the parallel: Exceeding this limit may introduce distortion, increase occlusions, and hinder the performance of detection, speed and near miss algorithms particularly to the edge of the camera view.
Benefits:
Consistent Image Capture:
Uniform Vehicle Appearance:
A low angle ensures vehicles maintain a consistent size and shape in the footage.
This consistency enhances the accuracy of detection algorithms and tracking.
Note: Our detection algorithms are trained on the 0-25° parallel angle. Moving outside of this will cause lower accuracy of detection.
Clear Front Profiles:.
Improves the system's ability to distinguish between different vehicle types by looking at grill and bumper configurations.
Minimised Motion Blur:
Reduced Relative Motion:
Lateral movement across the camera's field of view increases motion blur compared to vehicles moving directly toward or away from the camera.
Results in sharper images, essential for reliable detection and recognition.
Considerations for Perpendicular Angles:
Sometimes it is impossible to install the camera parallel to the roadway. In this case it is recommended to put the view as far back from the detection zone as practical while remaining within the detection range of the camera.
NOTE for Detecting Bicycles: When bicycles/eBikes are a primary object class it is better to use a perpendicular view versus parallel view. This side on view gives the software a larger number of pixels per meter of the bicycle than the thin frame when viewed from the front.
License Plate Recognition:
Introducing Angle Towards Traffic:
If capturing license plates is required, an angle must be introduced (less than 25°) facing oncoming or departing traffic may be necessary.
Provides a better view of the front or rear of vehicles where license plates are located.
Site Constraints:
Physical Limitations:
Obstacles or infrastructure may prevent ideal camera placement.
If unable to position the camera parallel, recalibrate the system to adapt to the new angle.
System Recalibration:
Adjust detection zones and sensitivity settings within the analytics platform.
Ensures continued accuracy in detection and monitoring.
Horizontal Tilt to Horizon (Roll Angle)
Maintaining correct horizontal alignment of cameras is crucial for the optimal performance of the AlphaX XVision Video Analytics Platform. The horizontal tilt, or roll angle, refers to the rotation of the camera around its lens axis.
Optimal Horizontal Tilt (Roll Angle): Keep the camera level, with less than +/-5° deviation from the true horizontal plane.
Importance for Accurate Object Classification
Prevents Image Distortion:
Proper alignment ensures vehicles are captured in their true shape and orientation.
Deviations can distort images, confusing detection algorithms and reducing classification accuracy.
Enhances Detection and Tracking Accuracy:
A level camera provides a stable reference frame, improving the system's ability to detect and track vehicles and other objects smoothly.
Minimises false detections and tracking errors caused by skewed images.
Effects of Excessive Deviation
Reduced Detection Performance:
Excessive tilt may cause the system to miss vehicles or incorrectly identify objects.
Impaired Classification:
Distorted images can lead to misclassification of vehicle types, affecting data reliability.
Recommendations
Use Leveling Tools:
Employ a spirit level or digital inclinometer during installation to ensure the camera is horizontally level.
Verify Alignment:
Check the live camera feed to confirm the horizon appears level and objects are upright.
Regular Maintenance:
Periodically inspect and adjust the camera to maintain proper alignment, as environmental factors may cause shifts over time.
By maintaining a horizontal tilt of less than 10°, you enhance the system's ability to accurately detect, classify, and track vehicles. Deviating from this recommendation can adversely affect the performance of the analytics software, leading to decreased reliability of your vehicle monitoring system.
Field of View (FOV)
The field of view determines how much of the scene the camera captures and directly impacts the system's ability to monitor and analyze vehicle movements effectively.
Determining the Field of View
Lens Selection:
Wide-Angle Lenses (e.g., 2.8mm focal length):
Advantages:
Offer a broad horizontal FOV, typically around 90° to 110°.
Suitable for monitoring large areas and multiple lanes simultaneously.
Disadvantages:
May introduce distortion at the edges (barrel distortion).
Objects at a distance may appear smaller, potentially affecting detection accuracy.
Applications:
Ideal for intersections or areas requiring comprehensive coverage.
Telephoto Lenses (e.g., 12mm focal length):
Advantages:
Provide a narrower FOV but greater magnification.
Capture detailed images of specific areas or lanes.
Disadvantages:
Limited coverage area requires precise alignment.
Less effective for monitoring multiple lanes without multiple cameras.
Applications:
Useful for toll booths or focused monitoring of entry/exit points.
Calculating FOV:
Formula:
Sensor Width: Physical width of the camera's image sensor, measured in millimeters.
Focal Length: Distance from the lens to the image sensor when focused on a distant object.
Adjustment Based on Specifications:
Use manufacturer specifications for accurate calculations.
Adjust lens selection to achieve the desired coverage and detail.
Practical Application of FOV
Ensuring Comprehensive Coverage:
Detection Zones:
The FOV should cover all lanes and areas where vehicle detection is required.
Avoid including irrelevant areas that could introduce false detections.
Avoiding Blind Spots:
Proper FOV ensures there are no gaps where vehicles could go undetected.
Overlapping FOVs from adjacent cameras can eliminate blind spots in larger setups.
Balancing Detail and Coverage:
Resolution Considerations:
Higher-resolution cameras can maintain image detail over wider FOVs.
Standard HD cameras may require a narrower FOV to ensure sufficient detail.
Software Corrections:
Use de-warping algorithms to correct distortion from wide-angle lenses.
Enhances detection accuracy by accurately representing object shapes.
Environmental Factors:
Lighting Variations:
Be mindful of how lighting changes across the FOV can affect image quality.
Utilise Wide Dynamic Range (WDR) features to handle high-contrast scenes.
Obstructions:
Ensure the FOV is free from physical barriers like trees or poles.
Regular maintenance may be required to keep the FOV clear.
By meticulously setting the camera viewing angles and field of view, you ensure that your vehicle monitoring system captures high-quality images necessary for accurate detection and analysis. Proper configuration of these parameters is essential for the optimal performance of the AlphaX XVision Video Analytics Platform.
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