Displaying of noise events
When the noise level exceeds a pre-set threshold level [normally around 60dB(A)] the monitor will start recording and saving the noise data.
If an aircraft appears to pass close to a monitor but does not display a noise reading, this may be due to a range of factors:
- the noise data has not yet been downloaded from the monitor (try again in 24 hours)
- the aircraft passed the monitor at a high altitude
- severe weather conditions (such as high wind) reduced the aircraft noise at the monitor below the threshold
- the monitor could be offline for upgrades or maintenance during the over-flight (as the monitors are exposed to the weather, regular maintenance is required to keep them accurate).
Some police movements are not shown on WebTrak due to the nature of these operations. In addition, a small number of aircraft movements are made without transponders and these also do not appear on WebTrak.
Data captured by WebTrak undergoes a daily checking process. This means that data in replay mode will be more accurate than in current flight mode.
The lateral accuracy (where an aircraft is over the ground) of WebTrak is dependent on the radar information the system uses. Radar can be inaccurate by small distances, depending on the aircraft’s distance from the radar and the type of aircraft movement. Airservices performance criteria for radar include thresholds for margins of error (tolerances).
WebTrak ‘smooths’ readings from individual radar points to show a consistent track. For scheduled flights which perform smooth turns, the lateral accuracy is better than 250 metres at 40 kilometres. For aircraft that make tight turns (for example, aerobatic aircraft or helicopters), the lateral accuracy is 450 m at 40 km. This means that aircraft may not have flown exactly on the track shown on WebTrak.
Height information is derived from changes in air pressure recorded by aircraft in flight. This is corrected for pressure variations at the ground during the flight. The margin of error using this method is 125 feet—so that at any one point, the aircraft may have been 125 ft higher or lower than the altitude shown on WebTrak. However, extreme weather conditions that cause rapid changes in pressure, such as the approach of a cold front, can further affect the accuracy of aircraft height measurements.
In extreme cases, WebTrak can give the impression that an aircraft has deviated off the runway. This is due to radar reflections that can occur at low altitudes. Some police movements are not shown on WebTrak due to the nature of these operations.
Liability and copyright
We have made every reasonable effort to ensure the information presented is accurate. However, the data within WebTrak may still contain inaccuracies in some cases. It should not be relied upon when making personal, legal or financial decisions.
WebTrak is provided for personal and non-commercial use. Users may not modify, copy, distribute or reproduce in any form the data obtained from WebTrak. All maps used by WebTrak are copyright.
Privacy: personal information
WebTrak does not collect or store any personally identifiable information. Some information on site usage is stored. This may include internet protocol addresses, browser types, platforms and pages processed. This information is used to analyse and improve the performance of WebTrak.