[1] The Parallax Aircraft Parking Aid is frequently combined with an AGNIS system, informing flight crews when to stop.
As this system relies on the position of the viewer, it will not give accurate distance information to aircraft which have deviated significantly from the stand centreline.
Used in combination with AGNIS at stands which can only accept smaller airliners, it features one or two mirrors, allowing the flightcrew to see ground markings in relation to their nose wheel, when it is within the area they need to stop.
[1] Advanced Visual Docking Guidance Systems feature electronic displays which perform the functions of an AGNIS/PAPA installation, although with much greater accuracy.
The azimuth guidance, based on the Moiré Pattern works independently of the laser that calculates distance to stop and is unaffected by weather conditions.
The green lights on the left and right of the display will begin to appear, from bottom to top, as the aircraft gets closer to the stop line.
The latest models developed by ADB Safegate are called Safedock X and Flex which provides advanced functionality including detection through radar system.