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The pilot of the Beechcraft Bonanza was conducting a Global Positioning System (GPS) instrument approach into Lilydale from waypoint "charlie" which was located 15 NM north of Lilydale. As the pilot approached waypoint "India", a position 5 NM south of "charlie", the controller advised the pilot that he was two and a half miles east of "charlie". When the pilot advised that he was just passing waypoint "india", the controller responded that he was not and that he was, in fact, two and a half miles east of "charlie".

The pilot decided not to follow the controllers information and conducted a missed approach. Just as the pilot commenced the missed approach procedure, he became visual and was able to visually establish that his position was accurate and, as he expected, on the GPS approach track. The pilot continued the approach visually.

The pilot later reported that he had checked all of the available information and had verified that he was tracking via the correct GPS track. When the controller advised him that he was 2.5 NM east of "charlie" the GPS indications were within 0.13 NM of waypoint "india". The pilot reported that he checked the GPS function with an accompanying pilot and found no error.

The investigation revealed that the controller had never seen this approach being flown in instrument meteorological conditions before. In an attempt to educate himself about the Lilydale GPS approach, the controller used the bearing and range line to graphically display the last two positions of the approach on the air situation display. The controller misread the approach plate and displayed incorrect waypoints on the air situation display. The controller used this incorrect display to provide positional information to the pilot.

Following this occurrence, Airservices Australia developed an electronic selectable map, based on verified data, available on the air situation display to display all of the waypoints associated with the Lilydale, Moorabbin and Avalon GPS approaches.

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