Bob,You are absolutely correct - actually this "perfect" accuracy during enroute phase bothered some scientists enough that one of them (my friend) working at NASA Ames wrote a scientific paper on the subject proposing so called "continuous altitude rule" - a rule that would set altitude based on your heading/course. You can read an abstract and the whole article here:http://www.aviationtoday.com/cgi/av/show_m...102feedback.htmI also like the idea of the random cross-track error.Michael J.NASA Ames

>>Equipped with GPS navigation, these two jets approached from>opposite directions on the same track and collided. >Regardless of any other pilot or ATC controller error, a>radio, or transponder, or TCAS, or other system failure, one>truth seems apparent to me: these two jets struck head on, in>part, because their navigation systems put them perfectly into>the same traffic lane, reducing their only hope for separation>to the vertical plane.>If I choose, my GPS driven auto-pilot will fly up to a mile from the centerline of an airway, etc. Otherwise, it might be within three feet or so. This feature was designed for conjested airways, although we'd normally figure altitude seperation for opposite directions.L.Adamson

>If I choose, my GPS driven auto-pilot will fly up to a mile>from the centerline of an airway, etc. Otherwise, it might be>within three feet or so. This feature was designed for>conjested airways, although we'd normally figure altitude>seperation for opposite directions.True, most (maybe all) GPS nav systems will do that, but in every jet I've flown it's been a real pain to setup and use, because the offset must be set for each leg manually. Works OK on the NATS with 45 min between waypoints, but not so well in busy airspace over land.The random offset function I would like to see would be automatic at all altitudes above the OROCA, and would set aircraft to fly a parallel course offset to right of track by a random cross-track distance of between 200-3000m to the right of track centerline. Airways are already designed to allow 4nm deviation left/right of track based on allowable error from much less accurate conventional terrestrial radio navaids.RegardsBob ScottATP IMEL Gulfstream II-III-IV-V L-300Santiago de Chile

Scott,From what you have set out there appears to have been abreakdown in some basic ATC procedures.Assuming the Brazillian ATC system is using ICAO procedures the both the Brazilia and Amazonica procedural controllers maintaining the 'Board' and doing the coordination for the radar controller, should have had a 'strip' on each aircraft under the boundary designator on their respective control positions. Also the strips would have been of a different colour or had some other distinguishing feature. Each strip should show clearly the current assigned level.It is also normal for coordination to take place between the two centres/controllers at least 10 minutes before the boundary position. So the Amazonica controller should have had a TERES position report and ETA for NABOL including the current assigned level of 370 for the GOL B738. A controllers normal action would be to check the times and level against any other strip under the boundary designator for a posible confliction. Similarly the Brazilia controller would have been given the TERES position eata NABOL for the Legacy jet. So at least one of the controllers should have picked up the conflict at the time of the position coordination. Also the radar controllers (if radar coverage existed) should be checking the mode C readout on the target labels. A possible scenario. Did the Amazonica controller advise the Brazilia controller during the coordination that he was going to assign the Legacy jet FL360 before the boundary and so the Brazilia controller wrote 360 on his strip for the Legacy jet??? And subsequently for whatever reason the Anazonica controller did not issue the level change instruction to the Legacy jet. But again even if the Brazilia controller had accepted the coordination, he would have told his radar controller that the Legacy jet has been assigned FL360. As soon as he had both aircraft on his display the first thing he should have checked was the mode C levels. If they were the same, do something about it. If there was no radar coverage in that area then there is no fall back, and as both aircraft would appear to have reached the NABOL at about the same time they would have been on different frequencies and the only safety net left was TCAS and or the Mark one eyeball which is not very reliable at these heights and speeds. All the little holes lined up!The ATC tapes, cockpit voice recorders and flight data recorders hopefully will eventually provide the answers to this unfortunate incident.NeilYPAD (retired ATC)