My wife is on a flight right now. LAX to JFK. I’m using a Flight Tracker website to track her progress- excellent way to know if there are delays, or if a tasty tailwind has pushed them home sooner than scheduled.
Why, exactly, is this information provided? What do the abbreviations in the first column stand for? How does a “Waypoint” differ from a “VOR-TAC (NAVAID)” in the last column? Now, I can appreciate why this information would be accessible to all carriers. The sky is big, but it isn’t THAT big since almost all commercial ( large-body ) aircraft travel in a fairly narrow slice of air, altitudinally speaking. One would like to program in a path that avoids other aircraft.
Having said that, why am I able to access all of that information- and what good would it do me?
And lastly, this. Are Longitude and Latitude measured equally regardless of altitude? If one imagines, say, a 20 foot diameter topographically accurate globe, I grew up thinking that the longitude and latitude lines did indeed crawl up and over the Andes, Rockies, Himalayas and so on- but that the measurements would be different depending on distance from Sea Level. Am I wrong here?
I’ll leave the details on waypoint vs. VOR-TAC navaids to the big iron and commercial pilots who will be able to provide a more concise and detailed answer than I could.
As to why it’s available - why not? It’s just the route the airplane takes, it’s no different than a highlighted route on, say, Google Maps for street travel. While it may not have a great deal of meaning to the average traveler I don’t see where providing it causes any harm and there are people who are both knowledgeable and curious who have their own reasons and pleasures in following such details.
VOR-TAC navaids = a physical place with equipment to send out signals for aircraft to use. Their positions are known & equipment on the A/C can tell you when you are at them.
Thew aircraft has equipment that can tell which radial or precise angle from the station, how far away you are from the station… Or you can tune into two stations at once and see that you are where two radials cross. that is one form of way point. A place in the sky you can be at, going to or going away from in a particular direction that can be noted by whatever tracking service you are using to keep track of that particular aircraft. Usually used to file flight plans. With GPS, I do believe some are just lat / long positions in the sky.
When reporting, a pilot would say that he is at xyz & that ppj is next in 24 minutes or some such.
With direct routing using GPS, transponders and other high tech stuff, the standard old fashioned IFR routes & way points are being replaced with more direct flights which means more aircraft can be going to the same place in even better safety.
In actual practice, it is simpler to do but more complicated keep track of and flight manager computers handle a lot of that load now.
Paging Richard P or another big iron drive who is up on the latest stuff to get all these little ducks in a row before they fall off the edge of the world. I’m not sure I even understand what I just said. he he he
I’m wondering why you think height above ground or sea level would change the longitude and latitude. In 3-dimensional, global space, your exact, precise position would be given by three coordinates: longitude, latitude, and height.
If a bad guy wanted to bring down a plane they wouldn’t need to find one on a flight tracking website.
Planes are often visible after they take off. Rattling the windows of homes near the airport. I hope a bad guy never gets a weapon like that inside the US.
I’m keeping this vague for a reason. I don’t want to type anymore details.
It’s only a matter of time and desire. The US has dumped hundreds Stinger anti-aircraft missiles around the world, not to mention an untold number of RPGs floating around.
Anyone who really wanted to get their hands on one probably could get it in to the US.
The fact that an aircraft hasn’t been blown up on takeoff is an indicator of one of two things…either our intelligence and security is so good that all attempts have failed, or there just aren’t that many people residing inthe US with the intent or will to blow up airplanes.
Actually, there was a DHL 747 that was struck by portable ground-based missile on take-off from Baghdad. Hit the plane, did damage, but the pilots managed a safe landing anyway. So it has happened, for real, just not in the US.
At any given speed, it would take longer to travel from one place (defined by latitude and longitude) to another at 30,000 feet (or any height) than it would at sea level.
Sure, but that’s why you need three dimensions to calculate the distance: longitude, latitude, and altitude. My longitude and latitude is the same whether I am sitting here or levitating in my hovercraft 30,000 feet above my house, right? Or am I missing something?
That’s pretty much it, the following is for anyone interested in more detail.
Some nomenclature is a bit fuzzy and FlightAware may make distinctions where there shouldn’t be any, for instance a waypoint is really any defined point in a flight plan that is known to both ATC and the pilot. It may be defined by a physical radio beacon on the ground or by reference to a physical beacon, it may also be defined as a lat/long with no corresponding physical beacon. Waypoints might be part of published airways routes and have plain language names or abbreviations of plain language names or they may be pure lat/long positions chosen specifically for a single flight. So a VORTAC and other physical beacons aren’t distinct from a waypoint, rather they are a type of waypoint.
Types of ground based beacons (navaids).
Civilians are interested in three types of beacons, the VOR, the DME, and the NDB.
The VOR is a VHF radio station that, when paired with suitable equipment on the aircraft, can display the radial the aircraft is on. A radial is the bearing from the ground stations as measured at the station (it can be a few degrees different to what you would measure at the aircraft due to the nature of great circle tracks.) A radial alone does not provide you with a position because you could be anywhere on that radial.
A DME (distance measuring equipment) is a VHF/UHF station that provides a reading of distance from the station to the aircraft. The distance is slant range rather than ground range, ie it is the direct distance to the aircraft and will measure the aircraft’s altitude in nautical miles when you are directly over the top of it. A single DME reading alone is not enough for a position as you could be anywhere on a 360º circle centred on the station.
An NDB is a very basic beacon that just transmits a signal that an ADF needle on the aircraft will point to. In its simplest form the needle in the aircraft just gives a relative bearing from the aircraft to the beacon, eg 10º left, 30º right of nose etc. Combined with information about the aircraft heading you get an absolute bearing typically measured relative to magnetic north. So the 10º left of nose becomes a bearing of 335º to the NDB if your heading was say 345º. A single NDB bearing is not enough for a position as you could be anywhere on that bearing.
As you can see, any single data point is not enough for a position fix but a suitable combination of any two is enough for a position fix. So it is common to see VORs paired with DMEs so you get a position expressed as a radial and distance from the station. When the DME is at the same place as the VOR they are said to be co-located. NDBs have largely been phased out in most parts of the world but they are still common in some backwaters including Australia. An NDB/DME is also suitable for a position fix. you can also get position fixes from combinations of VOR/VOR, DME/DME, VOR/NDB, and NDB/NDB. The caveat is that the closer the position lines are to right angles, the more accurate the position fix. The last four examples will not work if they are co-located.
The TAC part of a VOR/TAC is a military beacon known as a TACAN that includes DME. Civilian aircraft can’t use the bearing/radial information from a TACAN but they can use the DME. For civilian purposes a VOR/TAC is functionally identical to a VOR/DME.
Airways routes
In the good ol’ days, which weren’t that long ago, airways routes were regular routes used by aeroplanes to get from A to B. They were made up of waypoints that were defined by reference to VORs, NDBs, and DMEs. Some waypoints would be directly over the beacon itself and would have the name of that beacon, eg “AD” for the VOR/DME positioned close to Adelaide airport. Others would be defined with reference to a couple of beacons and would be termed “intersections”. Many airways routes were inefficient because they were partly constrained by the ability to physical build a radio station on the ground. you can only have a few hundred miles between radio beacons otherwise you would lose the signal and would have to rely on dead reckoning.
Along came GPS and navigation got a lot simpler and more flexible. A waypoint could be absolutely anywhere you want it to be. Aircraft could now be routed much more directly between airports. The improved accuracy also allowed for close spacing of routes so that opposite direction traffic could be on different routes without being so far from the direct track as to be impractical.
Ground based beacons are still in regular use because not all aircraft have GPS and GPS has a flaw in that it cannot easily report flaws in the validity of its position. This has been solved by using GPS receivers that compare the position solution from various combinations of satellites and can exclude satellites that it thinks are giving bad data. But this solution requires more satellites to be visible and it doesn’t solve the issue of what to do if the GPS position becomes unreliable.
Modern airways routes and navigation using GPS and FMCs
So modern routes are made up of a combination of ground based radio stations and lat/long positions not defined by ground stations. What actually happens in the aeroplane is that the GPS receiver, in light aircraft, or the flight management computer in larger more complex aircraft, contains a data base that includes the position of all of the ground based stations as well as the lat/long waypoints. We can navigate along routes technically defined by radio stations but actually just using the GPS. Good airmanship dictates that you have the ground based stations tuned and displayed but the reality is that the old network of radio stations, where it still exists, is becoming less and less visible to the pilots.
To further complicate matters, the FMCs actually automatically tune any ground stations in range as well as get position data via GPS receivers and compute a best position based on the geometry of all of the sensor inputs. Normally the GPS positions is given highest priority but sometimes a DME/DME position will be computed as being more accurate than the GPS and will be given higher priority.
inertial navigation/reference systems
Another navigation aid that has been in use for many years is the INS. The inertial navigation system starts at a known position, eg at the coordinates of bay 12 at LaLa airport, and by measuring all subsequent accelerations to the aircraft it can keep track of its position. The INS needs to be updated at regular intervals but allows for much longer range navigation than the old ground stations do. Now days the INS is just another input for the FMC to get a best computed position from.
The reason the INS did not have the same effect on navigation as GPS did, even though it has similar capabilities, is that it is a heavy complicated piece of equipment that is not available to the “every man” pilot. GPS was basically INS but more accurate, lighter, and cheaper.