In the approach zone to Amsterdam Schiphol Airport and in the area under the responsibility of general air traffic control, LVNL uses the Area Proximity Warning system.
When this function was introduced, it was configured in such a way that all traffic is displayed on the radar screen but with flights below a certain altitude – much of it so-called “general aviation” not directly managed by air traffic control – indicated using a smaller, dimmer symbol (icon) than those operating above this predetermined level. This difference ensures that the controller is not distracted by traffic he or she is not responsible for.
If and when such “uncontrolled” traffic does become relevant to controller’s operations, its symbol becomes bigger and brighter to draw attention to a potential unauthorised penetration of restricted airspace.
In the photograph below, the large track symbol represents flight AZA114 – an airliner. The two smaller ones are light aircraft flying below the altitude range for which the air traffic controller is responsible. But were they to climb into that range, their symbols would brighten and enlarge.
