GPS in a passenger jet

[Guest Khao Mun Gai]

signal inside the aircraft?

[Guest c_oflynn]

I'm told that if you hold it right at the window you can get a lock sometimes. Some airlines allow it, some don't.

 

-Colin

[Guest makaio]

During my recent trip to Virginia, I used my eTrex Legend at various intervals. The flight attendants kindly asked me to turn it off (more than once...OK, maybe 5 or 6 times ). I could only get a signal when it was against the window, so I'd place it against the window, pull the shade down over it, and let it sit there for 15/20 minutes. Seeing the track log over the background maps was cool. The best were those during takeoffs/landings. Also neat were the altitude and speed readings. I think we hit ~ 32000 feet and just over 500 mph at the fastest.

[Guest makaio]

During my recent trip to Virginia, I used my eTrex Legend at various intervals. The flight attendants kindly asked me to turn it off (more than once...OK, maybe 5 or 6 times ). I could only get a signal when it was against the window, so I'd place it against the window, pull the shade down over it, and let it sit there for 15/20 minutes. Seeing the track log over the background maps was cool. The best were those during takeoffs/landings. Also neat were the altitude and speed readings. I think we hit ~ 32000 feet and just over 500 mph at the fastest.

[Guest PneumaticDeath]

A good source of information about GPS receivers is Joe Mehaffey's site. In the FAQ, he talks about Is it safe to use in an airliner and Airlines which APPROVE or DISAPPROVE GPS use during flights

 

-- Mitch

[Guest kbraband]

There is also some previous discussion of this topic in another folder: http://forums.Groundspeak.com/ubb/Forum13/HTML/000203.html

[Guest wasmith]

I have used my Garmin Streetpilot and eMAP units on passenger jets and had a lot of fun with them. They must be held right against the window to get a signal and sometimes this is tricky. It's fun watching the moving map as I drive 490 miles per hour down the road beneath the plane. And yes I have had these units checked out by the flight crews and pilots, and they are not restricted.

[Guest Geoffrey]

What Ive done is to put an external antenna suction-cupped to the window, and the antenna connected to a Garmin 3 GPS. I would leave the GPS turned on, and in it's pouch, and that stuffed in my carry on under my feet. After take-off, i would take the GPS out of the carry-on and out of the Pouch to find it tracking good. Probably need to put the gps in a metal shielding box, to block any Electro-Magnetic interference from the unit.

[Guest Qman]

I flew Midwest Express on 7/31 and 8/1. They were on the list of airlines not approving. I asked, and they said no. I did check it out while we were on the ground and it worked fine when it was held against the window.

[Guest Khao Mun Gai]

Well - I did it!

 

We flew from Boston to Paris Wednesday night on Air France (not on either the approve or disapprove list).

 

It was a 767 with the seating arranged 2 3 2. My wife, daughter and I were together in the middle.

 

I tried the GPS from there and got nothing.

 

Fortunately, the flight was largely empty, so being the "chevalier" that I am, I offered to move to an empty "2" by the window so my wife and daughter would have more space. I brought my GPS with me.

 

It was very cool - all I had to do was touch a corner of the unit against the plastic shade and it would almost instantly acquire the satellites including WAAS.

 

I set a NAV to Paris and the unit drew the line across the Atlantic. It was smart enough to represent it as a curve on the high level map. The pilot's course was 3.8 miles off of the course indicated by the GPS.

 

I played with defining the data fields for each view and was able to monitor altitude (the GPS calls it "elevation"), speed (peak speed of 649), miles to go, estimated arrival time, etc.

 

Nice toy - nice way to kill some time on a 6+ hour flight.

[Guest brucebridges]

My Dentist was using a GPS on a flight, tapped into his computer. The Attendant approached and asked about it, left and the copilot came back to check it out, was amazed and sent the pilot back. They said he had a more sophisticated setup than they had in the cockpit. They let him use it with no problem after checking it out.

[Guest Dobre]

I've used mine all the time, never had any problems with the flight attendants (but I'm an airline employee!) How well it works depends on what kind of plane, and whether you are overwing (or in the case of turboprops underwing) or in front or back. I have had great readings during all phases of the flight with speeds over 550mph and landing at about 120.

[Guest Mike_Teague]

ttendant their flightplan route with their waypoints (I already knew it as I am quite an aviation enthusiast, but it was cool of him anyhow)

 

The other time I've used it was from Portland-Reno, on Southwest.. You can follow that flight in quite detail at my site below.

 

http://home.earthlink.net/~kvuo/aviation.html

[Guest SecretSpy]

My fiance and I used our Etrex Vista on our engagement trip and a trip to Vegas. It was very cool. On both trips (we flew Continental & Southwest) the stewardesses asked us about it but as soon as they found out that it was just a receiver & not a sender, they OK'd it. It was really neat to actually know where we were flying without being able to see the ground. It tracked our speed great but not our altitude as it uses the air pressure for calculations. It said we were at 8,000 feet (the cabin pressure). We just had to keep it next to the window for good reception. It's really fun & a great way to kill time on a long flight. I wish I had it on my trip to Alaska!

[Guest hfmcan34]

Not all GPS's will work in an airplane. I tried several times with my old 45 and could never get a reading. On a call to Garmin on another matter, I was told that the 45 software limits the allowable speed to 100 MPH. This was done to discourage pilots from using it and suing Garmin if they get lost. I recently used my III+ tied into my Dell Inspiron laptop with a 15.4" screen running Delorme Streets s/w. The cursor looked like a shooting star going across the color screen. We flew-at night- over a fire line from one of the many forest fires burning in the west. I saw on the screen (and through the window) the towns I had been reading about in a recent paper that was discussing the fires. From the air, the fires looked much too close the the lights of the towns. Airline was Northwest. No problem with use of the GPS or computer.

[Guest jpjazz]

On a recent trip to the East coast we had success using our MAP330 on a Delta Flight. Had to hold to window as discussed, but worked non the less.

[Guest Team JackQuest]

Recent trip to Alaska both Alaska Airlines and United mentioned GPSRs specifically in the "do not use during the flight" announcement. I always wondered if a handheld would lock at those air speeds. I had a friend who used one in his Cessna don't remember the GPSR model.

 

------------------

TEAM JackQuest (8H/11F)

Jack & Cyber

www.jackquest.com

Base Camp N 40° 20.268' W 75° 37.969' (WGS84)

[Guest bazooka]

Window seat, now I know what to do!

Got stuck in the middle of the plane the last two times I flew. My Mag315 never acquired.

Packed it with the luggage on the way home and wouldn't ya know, got a window seat. There was a pilot flying with the crowd so I asked him about its use. He understood they only receive but suggested to check the "can use/can't use" list. Wasn't on the list. This was on Continental.

[Guest bazooka]

Window seat, now I know what to do!

Got stuck in the middle of the plane the last two times I flew. My Mag315 never acquired.

Packed it with the luggage on the way home and wouldn't ya know, got a window seat. There was a pilot flying with the crowd so I asked him about its use. He understood they only receive but suggested to check the "can use/can't use" list. Wasn't on the list. This was on Continental.

[Guest quade]

Forget about using it IN the plane. We're using them OUTSIDE the plane!

 

See; http://groups.google.com/groups?q=gps&hl=en&group=rec.skydiving&safe=off&rnum=2&selm=9deqag%24qc0%240%40pita.alt.net

 

Paul

http://futurecam.com/skydive.html

[Guest Pote]

Two weeks ago I flew 6 segments on Delta with my GPSMAP76. It worked great, got WAAS diff. and everything. Never hassled by the flight attendents once. I didn't even have to hold up to the window all the time. Often I had 3 to 4 birds synched up from the tray table. I always had a window seat on the starboard side of the plane. I have 5 nice track if anyone wants them - for some reason I didn't get a track from Dallas to Mobile. It was extremely cool to look out of the window and identify the roads, lakes, cities and towns. She Who Must Be Obeyed actually wanted to switch seats w/ me so she could use it! If that's not a product endorsement for a piece of electronics, I don't know what is. Max speed - 598.5 mph, typical speed on the delta jets was around 540 mph. Interesting the pilot would come on the radio and say "we are at 28,000 feet, etc. etc." and the Map76 was saying something like 1500-2000 feet higher than the pilot. I haven't gotten a good answer as to why that is yet.

[Guest prv8eye]

rlines fly routes that are NOT a direct line. Someone going from Denver to Cleveland may wonder why his GPS says he's over Kansas.

 

Gus Morrow

Oceanside, CA

[Guest quade]

quote:

---

Originally posted by Pote:

Interesting the pilot would come on the radio and say "we are at 28,000 feet, etc. etc." and the Map76 was saying something like 1500-2000 feet higher than the pilot. I haven't gotten a good answer as to why that is yet.

---

 

There are at least a couple or three valid reasons for this;

 

1) Aircraft flying at or above 18,000 feet msl reset their altimeters to a reference of 29.92 inches of mercury. The reason for this is the assumption that they're jets and flying pretty gosh darn fast. So fast that if they constantly reset their altimeters to the local pressure that it would be a major hassle. By everyone setting their altimeters to 29.92, they have less risk of swapping paint. However, since the local pressure setting may be wildly different than 29.92, their real altitude may be greater or less than indicated.

 

2) ANY GPS datum is only that and doesn't exactly match up with the real world especially when it comes to MSL calculations.

 

Paul

Flight Instructor, Skydiver, Geocacher.

[Guest Pote]

Thanks quade. Sounds plausable. But don't the jet jockeys get their alt. adjustment from ground radar fixes? And is the alt. feet above ground, not feet above sealevel? Afterall, I guess the pilot would care more that he was 2500 feet above a 3000 foot mountain, rather than just being 2500 feet above sealevel? I know it's a moot point at 32,000.

 

As far as the GPS, I'll never trust the alt. figure anyway. I was on the Chesapeake Bay near the CBBT and my alt. was showing (minus) -46.3 feet. I knew better... ;^) And I had a big fat WAAS lock on 3D Diff.

[Guest peter]

quote:

---

Originally posted by Pote:

Thanks quade. Sounds plausable. But don't the jet jockeys get their alt. adjustment from ground radar fixes? And is the alt. feet above ground, not feet above sealevel? Afterall, I guess the pilot would care more that he was 2500 feet above a 3000 foot mountain, rather than just being 2500 feet above sealevel? I know it's a moot point at 32,000.

---

 

Well I'd trust the GPS reading more than the plane's altimeter if what you want is true elevation above sealevel. The GPSR reading should be within about 50-100' when you have a good signal from 5 or more dispersed satellites. Paul is right that when above 18000' the pilots set their barometric altimeters for a 'standard' sealevel pressure of 29.92" and assuming the standard atmospheric model of temperature lapse rate with altitude. Neither of these standard models is likely to be right, but it doesn't matter as long as everybody else's altimter in that area is off by the same amount. That way the guy flying at an indicated 32000' won't collide with the guy at 34000' even if both of their altimeters are off by a couple thousand feet.

 

Now when they descend below 18000' and are getting ready to land, then they do want numbers that are close to reality so they don't fly over a mountain or antenna tower with insufficient clearance. At that point they get data based on the current barometer reading on the ground where the airport is and adjust their altimeter accordingly.

[Guest Hallatauer]

I think the major thing that the airlines are missing here is that a GPS receiver is just that.. a receiver. Like a radio receiver it doesn't transmit any electronic waves only gathers in the signals out there and uses them to process information. The problem with laptop computers is that the displays on them emit radio waves that have been identified as interfering with a planes navigation system. The "turn off all electronic equipment" announcements the airlines use is probably to make it easier for the flight attendants. They don't need to differentiate between a laptop, a walkie talkie or a GPS, just turn them all off please.

 

GPS is being used more and more in the airline industry. I work air traffic control from New York and we also cover a large piece of airspace over the north atlantic ocean beyond radar coverage and that is being slated to go mandatory GPS with datalink within the next 3 years or so. The idea being that every 30 seconds a GPS receiver will transmit the aircrafts position, the altitude coming form the alitmeter, via datalink to our computer which will gives us a position on a display. This will greatly enhance the accuracy and therefore ease the minimum spearation stardards we have to abide by. Presently a properly maintained altimeter is more accurate than a GPS receiver and I don't ever expect them to ease the minimum 1,000ft separation standard any lower. It is very tight as it is and I'd think we'd all like to leave a little margin for error. Note: Sitting in my backyard with a known 95ft above sea level, my Magellan 315 bounces between 80 and 125ft on average.

 

If interested in looking at a world map or glode, the airspace I work is from 45,00N 40,00W - 18,00N 40,00W - 18,00N 60,00W - 23,30N 60,00W - 25,00N 73,00W, then roughly follows 120 miles off the US coastline to just east of Nantucket Island 41,30N 67,00W and back to starting point. Alot more planes fly through here than you might imagine. The Europeans love the carribean.

 

 

------------------

Dan McLauglin

40 46.802N

73 07.630W

[Guest PneumaticDeath]

ic altimeters, and if you want to know your "real" altitude, you need to calibrate them for the local pressure.

 

If you know that there is a 3000ft high mountain somewhere near where you're going to be flying you'd better stay at 4000ft. I believe that FARs require pilots to keep their aircraft at least 1000 ft. AGL (above ground level) except during takoff and landing, or with special permission.)

 

-- Mitch

[Guest PneumaticDeath]

quote:

---

Originally posted by Hallatauer:

I think the major thing that the airlines are missing here is that a GPS receiver is just that.. a receiver. Like a radio receiver it doesn't transmit any electronic waves only gathers in the signals out there and uses them to process information.

---

 

That's a popular misconception. Every radio receiver also re-radiates some energy. The tuning circuts have to have a lot of reference frequencies to use. This is why am/fm radios aren't allowed on commercial flights.

 

While the amount radiated by GPSRs is small, you've got to remember the inverse square law. You're could be only 40 or 50 ft from the receiving antenna, and the signal they're trying to receive is coming from 10's or 100's of miles away, meaning that if the GPSR is ratiating 1mW (1/1000th of a watt), it woud be as strong as a 100 KW station 100 miles away. Now, for the most part, GPSR radiate in bands that aren't used for aircraft navigation, but new designs could be different.

 

What about the GPSRs used on aircraft already? They've been tested, and are known not to interfere. The same can't be said of the little handheld units. Like others have said.. never presume that you know more about the aircraft than the pilot. Maybe you do, maybe you don't.. but the responsibility of keeping 400 people alive is his or hers, not yours.

 

Read more about all of this are Joe Mehaffeys site.

 

-- Mitch

 

[This message has been edited by PneumaticDeath (edited 22 August 2001).]

[Guest Geoffrey]

Probably cant bring a GPS in carry-on luggage anymore. They are making it harder to do anything now.

[Guest Prime Suspect]

quote:

---

Originally posted by Geoffrey:

Probably cant bring a GPS in carry-on luggage anymore. They are making it harder to do anything now.

---

 

Yesterday on NPR I heard for the first time, speculation that a hand-held GPS unit may have been used to assist the hijackers to their targets. For the time being, I think it would probably be prudent to leave the GPS packed away in your bags.

[Guest Cermak]

I too have used mine on a plane just to get an idea of the speed and altitude. We were going from Chicago to Dallas and it registered 515mph at about 37,000 feet. Pretty interesting, but it will probably be the one and only time I use it.