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Guiding Air Traffic Sans Radar With GPS
CamMac writes: "UPS Aviation Technologies, a subsidiary of UPS, helped in developing a new air traffic control system called ADS-B in which the aircraft broadcast their position, altitude, and airspeed to each other and the ground based on GPS data. This is all done without radar, so it is effective in remote areas or in mountainous terrain. It also displays all this information to pilots as well as ground control, so that aircraft are no longer dependant upon crypic orders from the gound to understand where everyone else in the sky is." Besides being a smart way to take advantage of all those GPS satellites, this also lends plotline cues for remakes of such classic cinema as Goldeneye, Diehard II and Airplane.
Indeed. I hat things that are har to undersand.
Never meant half of the things I said to you. So you know, there's a half that might be true - G. Phillips
Lans' system had an accuracy in the decimeter range (tenth of a yard) BEFORE the US DOD stopped fuzzying the GPS signal. This was achieved by a STDMA datalink (Self organising Time Division Multiple Access) and adding a few (there are currently around 30 of them covering Sweden, a country roughly the size of California) land-based transponder stations to the satellite coverage. The system basically use the land-based stations to enhance the satellite data. It is mature, operational and is an ITU and IMO world standard for large ships.
On the terrorist/security aspect, I'd just like to point out that all civilian and military aircraft are required to carry and operate radar transponders at all times while in 'civilian' airspace so this system doesn't change anything in that respect.
In short - it's a great system and everyone should use it; but it's hardly news.
This seems like a really bad idea to me. It's practically an engraved invitation to someone to modify or create a version of the GPS system that spews bad data into the network.
When will these guys figure out that you absolutely cannot, under any circumstances, trust externally supplied data. You cannot safely use any data from an outside source in your computations--and these guys are going to go and make our entire air infrastructure run on a trust model?
The mind boggles.
daniel
All I needed to know in life I learned from
Not exactly. The Traffic Collision Avoidance System (TCAS) is an aircraft-to-aircraft system that works from a multitude of input data (as practically every on-board system does) to determine with the largest precision & accuracy the location of the airplane which is then broadcast out to other TCAS receivers in an attempt to avoid collisions.
Each TCAS receiver classifies incoming data in various levels: No Threat, Proximity, Traffic Alert, Response (?) Alert - which in aviation lingo translates to TAs (Traffic Alert) and RAs (Response Alert). The TAs and RAs are the only things of significance to the pilot since they are potential collisions (especially the RAs) - hence their color on the navigational and primary flight displays: yellow for TAs and red for RAs.
Based on his current flight (ascending, descending, level) the pilot keys in the TCAS system to show him only tracks of interest - if he's ascending, it makes no difference what's below him, etc.
This system is based on ground location data (from a multitude of sources, all based on radio towers located on the ground, with known positions) GPS data and differential GPS (where available - the only flight system I'm aware of that uses this in the US is the Boeing 777 with Honeywell's flight management computer (FMC) and Honeywell's large format display systems (LFDS) - similar to what was posted about the new shuttle display systems here on /. not too long ago.
Differential GPS is primarily only used for approaches, I believe - since that's the only time more precision than GPS is necessary (and even after the military scrambling of GPS ended, more precision is necessary to land the plane than military GPS provides) - 10 meter accuracy (or whatever it is exactly) puts you on the runway or off of it - not nearly enough for the autoland systems to feel comfortable with!
My reference: ex-avionics engineer for Rockwell Collins. That said, none of the statements made (express or implied) reflect the position, past or present, or presume to be 'expert advice' in any matters avionic, of Rockwell International Corp.
- This particular implementation is curently being tested in parts of Alaska where there is little to no radar coverage. While the system might not offer all the features of radar coverage, its a lot better than what's there now.
- All GPS's certified by the FAA for use in aircraft report altitude. In addition to use the GPS data to compute the altitude, many GPS units can also connect to the altimiter for altitude data just as MODE C transponders do now. Since selective availibility has been turned off, gps computed altitude is very accurate.
- Having the GPS report the aircraft's position for purposes of aircraft seperation is just one small part of this. The UPS technology allows for two way data tranmition between the aircraft and the ground. This is useful for uploding weather data to aircraft, something that is only currently available as an option on very high end corporate and commercial jets. The GPS simply says, "I'm here" and the bandwidth usage is minimized by only sending the data for the local area (as well as any pireps, sigmets, or other timely information). For what its worth, you can also check your email.
This system was never intended to replace ground based radar as a means for directing air traffic. While a single failed transponder can cause problems in the current system, a failed gps unit on a single aircraft in a GPS only system could be catostrophic.If you think this is cool, take a look at http://www.flightexplorer.com. it allows you to track flights in real time. Not just scheduled airliner traffic, but your friend in his Piper Cub.
Or should we say it is *a* differential GPS. DGPS is a standard system that does not come close to the 8" or so accuracy of the Lans system. (The best i've ever seen with DGPS even since SA was turned off has been 3ft.)
Basically the lans system used DGPS data (diference in actual vs reported position from each bird) plus clock error data plus a higher density of differential stations. Of course this required expensive atomic clocks at each differential station and a very complicated (though not terribly expensive) reciever, but it certainly wasnt DGPS. And YES the US did try to supress installations of that system in this country as it took gps out of government control (e.g. if you lost satellite reception entirely, you could still possibly deduce your position from land-based recievers alone) where with DGPS you still had to have satellite communications.
~GoRK
For several reasons. First of all, on smaller aircraft, standard altimeters require constant attention from the pilot. The altimeter gets its data from comparing the pressure of the air outside the plane to the pressure of the air on the ground, and then doing some math to figure out the altitude. The problem is that the altimeter has to know what the pressure on the ground is. This is achieved through a small dial on the side of the altimeter that the pilot has to adjust every 15 minutes or so to keep it accurate. As you can imagine, this is prone to error, and added workload for the pilot.
Secondly, standard altimeters have a tendency to break. I've only been flying for a few years and have already run across several dead or dying altimeters that have required me to change my flight plans.
So I think GPS-based altitude (and this GPS system in general) is a long-needed treat for the aviation community. There are a few hurdles that need to be crossed, such as avoiding abuse of the system (I believe someone else already posted about this) and redundancy. But if they can get the flaws worked out of the system on the ground, I for one will be happy to fly with it in the air.
kugano
It can, since all you are really doing is just triangilating on another axis. Most of the low-end consumer devices can report alt., although the accuracy seems to vary from bad to not-so-bad. High end devices should be more likely to provide accurate alt. info, although it really depends on how many satellites are in "view" (the more the better).
I could see how GPS would be good enough to navigate by, but probably isn't good enough land by (yet).
Someday a Slashdot ID of 177180 will mean something.
Ahhhh! Gnutella for Gnavigation!
"I will gladly pay you today, sir, and eat up
Sacred cows make the best burgers.
The fuzzy factor imposed by the US government to thwart military uses of their GPS system was lifted on May 1 of this year (see http://abcnews.go.com /sections/tech/dailynews/gps_000501.html) - making the use of GPS 10 times more accurate. So, GPS, even for folks like us, is now accurate to within 20 yards. Plus, airplance don't have too many things in their way to block signals from those satellites.
I think you picked the wrong James Bond movie - especially given that "Tomorrow Never Dies" plotline involved changing the syncing of the GPS satellites in order to send a ship into Chinese waters to start a war. Obviously some sixth sense working but only on half power :-)
Cheers,
Toby Haynes
Anything I post is strictly my own thoughts and doesn't necessarily have anything to do with the opinions of IBM.