Airfield Activity Monitoring and Analysis System

This application note outlines a technical concept for a system designed to monitor and record incoming and outgoing aircraft movements on any airfield.  Movements will be recorded by cameras on a continual basis without the need for operator intervention.  Should an event occur worthy of review then recorded video footage can be replayed and detailed analysis, including 3D position and trajectory, of the aircraft(s) can be determined.

 

Diagram 1 below, shows the overall concept of the system. Click to enlarge.Diagram 1

The system employs two pairs (four in total) of high-resolution digital cameras at each end of the runway.  All cameras will look from the end of the runway out into the take/off or landing corridor.  One pair of cameras use a lens optimised for image capture up to 1km from camera position and the other pair use a lens optimised for image capture up to 3km away.

Video data from all cameras is routed to a computer with large storage capacity.  This computer records all video data for a period of 24 hours, after which stored video data will be overwritten.  

Once installed this system runs continuously without the need for operator intervention.

If an event occurs then an operator is required to review the recorded footage and find the section of video of interest.  Please note, the operator has 24 hours from the event occurring to find and isolate the footage for further analysis.

The operator is then able to perform further analysis of the event.  This is achieved by with the use of motion analysis software, which is also installed on the Workstation.

The software uses advanced optical tracking algorithms, which allows the user to track objects as they move within the image field of view.  Providing the location of the cameras is known and a common frame of reference is used the data obtained can show a 3D position and trajectory with high accuracy.  The software can track multiple points in the image, so 3D and trajectory information can be determined for multiple aircraft providing they can be seen by both cameras in the pair.  

Other data can also be computed, for example absolute velocity of the aircraft, separation between multiple aircraft and deviations of an aircraft's trajectory from a known path.  The data obtained when using the software can be saved and be used to produce reports and/or presentations.

Analysis

The effectiveness of the overall system is determined by the accuracy to which the software can determine the 3D position of the object being tracked.  There are several factors, which contribute to the accuracy of this measurement including location of cameras, resolution of the cameras, lens focal length (optical field of view at a given distance) and the accuracy of the survey frame of reference.

Photo-Sonics have considered all of the above parameters however, every airfield will be different so in order to get the best results the optimum location of cameras and lens focal length would need to be determined for each airfield.

The system requires a common frame of reference and Photo-Sonics suggest an (x,y,z) Cartesian coordinate system with the origin centred at the centre/end of the runway.  All calculated 3D positions would be with respect to this origin.

Diagram 2

The system would consists of digital cameras operating at 15Hz with a resolution of 1400 x 1000 pixels.  One pair of cameras have a 70mm lens, these cameras will provide a 3D measurement range from the end of the runway out to a range of 1km (please see diagram 3 below)

 

Diagram 3

Diagram 3 shows the available 3D measurement volume with a 70mm lens.

The second pair of cameras also have a resolution of 1400 x 1000 pixels and operate at 15Hz.  They employ a 105mm lens and produce a measurement volume from 500m to 3km, please refer to diagram 4 below.

Diagram 4
Diagram 4 shows the available 3D measurement volume with a 105mm lens..

To provide optimum triangulation accuracy the cameras should be located +/-250 metres off to the side of the end of the runway and 1km behind the runway end.  Both pairs of cameras should be located in the same place.  Any deviation in the location will result in degradation in the 3D position accuracy.

The optimum field of view for analysis at 1km will be 130 x 100 metres and at 3km will be 320 x 240 metres.

The resulting maximum 3D positional accuracy will be 4m in x, 0.5m in y and 0.5m in z.  The error in x improves significantly when the slant range to target is reduced.

The system uses readily available COTS hardware and software and can be easily configured to individual requirements.  If you have any interest in such a system or would like to discuss this subject some more please click here to contact our Sales specialists at Photo-Sonics International Ltd.

 

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