ALexeu
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GPS Coverage In Flight

Wed Jul 09, 2008 9:49 am

Even though using personal GPS is safe and legal, is it worth trying to catch satellites in mid-air (without WAAS) ? Are there any tips for having better GPS coverage in mid-air (I use Garmin eTrex Legend c) ?

Regards, Alex

[Edited 2008-07-09 02:49:43]
 
wilco737
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RE: GPS Coverage In Flight

Wed Jul 09, 2008 11:30 am



Quoting AlexEU (Thread starter):

Hi there,

I have a Garmin myself and used it serveral times in the cockpit. But only when I had the GPS near the window. When I had it in my hands the signal was already low, but still enough. The accuracy got down as well then. Within the cabin I have never tried it...

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David L
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RE: GPS Coverage In Flight

Wed Jul 09, 2008 1:18 pm



Quoting WILCO737 (Reply 1):
Within the cabin I have never tried it...

I have (in cruise only, of course  Smile ). It works well most of the time while you hold it up to the window. I even managed to get it to work through Concorde's tiny windows. Occasionally there aren't enough satellites "in view" but it's not much of a problem. If your receiver gives you a diagram of the satellite locations and signal strengths, you can move it around the window to get the best reception.
 
jgarrido
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RE: GPS Coverage In Flight

Thu Jul 10, 2008 6:00 am

I was able to get a signal with my garmin 60csx while sitting in a window seat. I held up to the window to get a lock then I was able to use with it sitting on the arm rest. The 60csx is one of the more sensitive units on the market though.

http://www.flickr.com/photos/jgarrido/2203117434/
 
ALexeu
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RE: GPS Coverage In Flight

Fri Jul 11, 2008 8:52 am



Quoting WILCO737 (Reply 1):
Hi there,

I have a Garmin myself and used it serveral times in the cockpit. But only when I had the GPS near the window. When I had it in my hands the signal was already low, but still enough. The accuracy got down as well then. Within the cabin I have never tried it...

Hi, but I will fly in pax cabin  blush 
As for the aircraft's GPS, AFAIK they have antenna, but I understood that you used personal GPS.

Quoting David L (Reply 2):
I have (in cruise only, of course Smile )

Is it a problem to use it on take-offs and landings? I have no intentions on doing that, but I am just curious how would f/a react.

Cheers, Alex
 
wilco737
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RE: GPS Coverage In Flight

Fri Jul 11, 2008 9:32 am



Quoting AlexEU (Reply 4):
As for the aircraft's GPS, AFAIK they have antenna, but I understood that you used personal GPS.

I was talking about the normel Garmin GPS you can buy in shops and not the built in GPS of the aircraft  Wink

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jgarrido
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RE: GPS Coverage In Flight

Fri Jul 11, 2008 5:50 pm



Quoting AlexEU (Reply 4):
Is it a problem to use it on take-offs and landings? I have no intentions on doing that, but I am just curious how would f/a react.

I forgot to turn mine off, and I guess none of the FA's noticed it. And I'm here to talk about it.

 
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DocLightning
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RE: GPS Coverage In Flight

Sat Jul 12, 2008 5:02 pm

I've *ahem* "forgotten" to turn mine off on a few flights. Including T/O and landing. I'm still breathing.

Yeah, they work if you wander around outside the airport first to make sure it has a lock on all the satellites. If your first use of the GPS for the day is in the cabin next to the window, lots of luck getting a signal...and even when you do, as soon as the plane turns around on the tarmac, you'll lose it.

On my LHR-JFK flight we rotated at 152 MPH and left the runway at 160 MPH.
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
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bond007
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RE: GPS Coverage In Flight

Sat Jul 12, 2008 5:41 pm



Quoting Jgarrido (Reply 6):
And I'm here to talk about it.



Quoting DocLightning (Reply 7):
I'm still breathing.

Yes, I've not worn by car seatbelt a few times, and am still here ... I know a couple of folks that aren't though, and would have been if they had worn it. Hardly a sensible reply about whether it's legal and/or a problem.

The bottom line is that best case (in the US anyway), a handheld GPS is allowed in cruise only, and only if specifically mentioned by the airline - since by default, it's a device that recieves/transmits, and these are generally only allowed on the ground, e.g. cellphones.

Some, if not most airlines, do specifically allow them during cruise only.

Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
David L
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RE: GPS Coverage In Flight

Sat Jul 12, 2008 8:36 pm



Quoting AlexEU (Reply 4):
Is it a problem to use it on take-offs and landings? I have no intentions on doing that, but I am just curious how would f/a react

As Bond007 says, it's not a limitation of the receiver but a regulatory issue concerning the use of electronic devices during take-off and landing.
 
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DocLightning
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RE: GPS Coverage In Flight

Sat Jul 12, 2008 9:54 pm



Quoting Bond007 (Reply 8):
The bottom line is that best case (in the US anyway), a handheld GPS is allowed in cruise only, and only if specifically mentioned by the airline - since by default, it's a device that recieves/transmits, and these are generally only allowed on the ground, e.g. cellphones.

A GPS does not transmit. It receives.

Now, a pacemaker sometimes transmits.
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
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bond007
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RE: GPS Coverage In Flight

Sun Jul 13, 2008 2:43 am



Quoting DocLightning (Reply 10):
A GPS does not transmit. It receives.

Yes, I'm quite aware. It's a device that either receives or transmits (receives/transmits?).

....although the electronic guys will tell you that a receiver circuit, by design, actually does transmit ... but that isn't what I meant  Wink

Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
bond007
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RE: GPS Coverage In Flight

Sun Jul 13, 2008 1:01 pm



Quoting Bond007 (Reply 11):
a receiver circuit, by design, actually does transmit

Hence the reason that receive only devices are generally prohibitied of course ... because they do in fact transmit (a tiny amount anyway), otherwise they'd be no reason to distinguish them from say, an Ipod or laptop.

Of course, I'm sure 90% of the folks who use laptops in flight, leave the bluetooth and/or wireless turned on, which no doubt cause many more signals than a radio receiver. .. but that's another story  Wink


Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
David L
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RE: GPS Coverage In Flight

Sun Jul 13, 2008 4:15 pm



Quoting Bond007 (Reply 12):
Hence the reason that receive only devices are generally prohibitied of course ...

I'm not sure receive-only devices are prohibited on any airlines I've flown recently. BA, for example, certainly seems to allow the use of radio and GPS receivers and even Bluetooth during cruise. Phones and other transmitters must be switched off at all times, of course.
 
ALexeu
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RE: GPS Coverage In Flight

Sun Jul 13, 2008 5:17 pm



Quoting Jgarrido (Reply 6):
I forgot to turn mine off, and I guess none of the FA's noticed it. And I'm here to talk about it.

Wow, which program did you use to exchange your route to google earth?

Quoting DocLightning (Reply 7):
I've *ahem* "forgotten" to turn mine off on a few flights. Including T/O and landing. I'm still breathing.

If you forgot to turn it off, where did you keep it, and how did you still receive signal? I am sure you didn't bother to hold your hand against the window...
 
bond007
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RE: GPS Coverage In Flight

Sun Jul 13, 2008 6:25 pm



Quoting David L (Reply 13):
I'm not sure receive-only devices are prohibited on any airlines I've flown recently.

Yes, I should always prefix my comments with "US Airlines"  Wink

But, even in the USA, it's still up to individual airline to allow or disallow certain devices, so I was just making a generalization.

Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
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DocLightning
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RE: GPS Coverage In Flight

Mon Jul 14, 2008 3:51 pm



Quoting AlexEU (Reply 14):
If you forgot to turn it off, where did you keep it, and how did you still receive signal? I am sure you didn't bother to hold your hand against the window...

I might have accidentally done so...

Look, the human body also generates an EM field from all of the transmembrane membrane gradients.
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"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
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ALexeu
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RE: GPS Coverage In Flight

Mon Jul 14, 2008 5:22 pm



Quoting DocLightning (Reply 16):
I might have accidentally done so...

Look, the human body also generates an EM field from all of the transmembrane membrane gradients.

It happened to me also, but the question is how could it possibly receive signal unless you held it near the window (which you couldn't do if you thought that it's off)...  Smile
 
MD11Engineer
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RE: GPS Coverage In Flight

Mon Jul 14, 2008 8:27 pm



Quoting DocLightning (Reply 10):
Quoting Bond007 (Reply 8):
The bottom line is that best case (in the US anyway), a handheld GPS is allowed in cruise only, and only if specifically mentioned by the airline - since by default, it's a device that recieves/transmits, and these are generally only allowed on the ground, e.g. cellphones.

A GPS does not transmit. It receives.

Any receiver, except for the very simple, insensitive detectors used in the 1920s, contains at least one oscillator for the intermediate frequency (in many cases two). These oscillators can radiate electromagnetic energy.
GPS receivers also contain a computer, which uses an oscillator for it's internal timebase.
The frequencies produced by these oscillators are in the frequency range of VHF navigation and communication systems.

Any coaxial cable (antenna cable, data bus, synchro line) in the plane, which by chance hasn't been shielded properly, can receive these signals and forward them to the avionics.
I'm currently doing a B757 EASA B1 level 3 course (as a refresher and because the FAA approved course I have done before doesn't get recognised by the EASA).
Our instructor told us of a puzzling problem with flap assymetry warnings in flight, leading to overspeed landings, where after many weeks of troubleshooting, they found a damaged data bus cable of the passenger entertainment system giving a wrong signal to the flap position transmitter circuit.
A mobile phone or another transmitting device (and any superheterodyne or audion receiver can radiate electromagnetic waves too), could also cause such problems .

Jan
Je Suis Charlie et je suis Ahmet aussi
 
jgarrido
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RE: GPS Coverage In Flight

Mon Jul 14, 2008 11:40 pm

Comparing a GPS the lack of seat belt? really? It's near univerasally accepted

Quoting AlexEU (Reply 14):
Wow, which program did you use to exchange your route to google earth?

http://www.gpsvisualizer.com/

it has lots of neat stuff you can do with gps track logs.
 
Malmi18
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RE: GPS Coverage In Flight

Wed Aug 20, 2008 5:53 pm

I have tried a Garmin Etrex in passenger cabin during cruise. It had been on last time on a different continent so definitely it had no useful location in its memory to start the search from. But it found quickly the satellites and our location after I put it against the window.

I had to test a myth that says the GPS manufacturers restrict the speed and altitude display below the values that are needed in jet airplanes in order to sell more expensive models to aviators. => BUSTED.  Wink

Another point is then that I suppose there is no legal way to use Etrex in a plane for any meaningful purpose.

Cheers!
 
thegreatchecko
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RE: GPS Coverage In Flight

Thu Aug 21, 2008 6:43 pm

I work at an airline where GPS units are prohibited at all times (cell phones as well). Its nothing personal. Simply, the airline hasn't had the time nor the resources to prove that these devices will not cause interference.

Is it going to cause the plane to crash, probably not, but will the FA ask you to turn it off, yes. So please just listen to the FA's, it just creates more paperwork when you don't.

Quoting Malmi18 (Reply 20):
I had to test a myth that says the GPS manufacturers restrict the speed and altitude display below the values that are needed in jet airplanes in order to sell more expensive models to aviators. => BUSTED.

The reason that they are more expensive is that they are "approved." Same reason that aircraft parts are more expensive. An alternator on a Cessna is pretty much the same alternator that can be bought at the local auto parts store, it just lacks the approval numbers. While it would work in the plane, don't let the local authorities find out, or you'll probably be looking at some fines and possibly action against your certificate.
"A pilot's plane she is. She will love you if you deserve it, and try to kill you if you don't...She is the Mighty Q400"
 
iairallie
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RE: GPS Coverage In Flight

Thu Aug 21, 2008 7:16 pm



Quoting Bond007 (Reply 15):
But, even in the USA, it's still up to individual airline to allow or disallow certain devices, so I was just making a generalization.

Every US carrier I've worked for specifically prohibited GPS use at all in flight even in cruise.

The rule of thumb is if it sends and/or recieves a signal it is not permitted at all. With a few exceptions.
Enough about flying lets talk about me!
 
sprout5199
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RE: GPS Coverage In Flight

Thu Aug 21, 2008 8:18 pm



Quoting MD11Engineer (Reply 18):
The frequencies produced by these oscillators are in the frequency range of VHF navigation and communication systems.

Naa, most osc's are in the 10 to 25 MHZ range. It is hard to make a VHF osc stable. Much easier too make a say 16.5Mhz crystal, and mulitply it to get the Freq you need. One of the biggest problems is harmonics. Even if you filter and supress the main freq, the fith or sixth harmonic may actually be bigger than the second or third(have actually seen that in a mistuned radio).

Dan in Jupiter
 
320tech
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RE: GPS Coverage In Flight

Fri Aug 22, 2008 2:12 am

My laptop transmits on VHF frequencies, to a distance of three or four feet. However, it's just putting out noise, not a signal, so it shouldn't affect anything (in theory). I also have an MP3 player (not an iPod) which apparently can transmit on transponder frequencies.

No reason why a gps should be any different. It probably transmits a weak signal that in theory can't do any harm. But if the FA says turn it off, then that is the final word.
The primary function of the design engineer is to make things difficult for the manufacturer and impossible for the AME.
 
jcavinato
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RE: GPS Coverage In Flight

Sun Aug 24, 2008 2:57 pm

Last time I was on a Southwest Airlines flight (about three or four months ago) their in-flight magazine stated that a GPS was OK to use. I was surprised to see a specific permission like that.
 
nomadd22
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RE: GPS Coverage In Flight

Sun Aug 24, 2008 4:05 pm

Your brain transmits emf. Shuffling across the carpet transmits emf. The cockroaches in Northwest's planes transmit emf. You can't just put a blanket prohibition on anything that transmits. The signal it puts out has to be significant enough to have some possibility of affecting systems, and GPS recievers don't put out anything near that much.
Airlines have policies to turn pretty much all electronic devices off because despite some nitwits expectation that every flight attendant should have every one of the 14 million devices and their emf characteristics memorized so they'll know if they're potentially dangerous, it's probably not going to happen.
Anon
 
MD11Engineer
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RE: GPS Coverage In Flight

Sun Aug 24, 2008 7:17 pm



Quoting 320tech (Reply 24):
My laptop transmits on VHF frequencies, to a distance of three or four feet. However, it's just putting out noise, not a signal, so it shouldn't affect anything (in theory).

White noise is an extremely broadbanded signal, which basically includes all frequencies and can actually jam a whole frequency band (if transmitted strongly enough).

E.g. the new "internet via the powerline LAN" systems emit a very broadbanded noise, which blocks the whole HF band in a radius of several hundred meters from the house where the system is installed.

Similarly military "over the horizon" radars block whole bands, often in the frequency range reserved for radio amateurs (probably because the relevant authorities think that radio hams can't complain).

Jan
Je Suis Charlie et je suis Ahmet aussi
 
iairallie
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RE: GPS Coverage In Flight

Mon Aug 25, 2008 4:35 am



Quoting Nomadd22 (Reply 26):
You can't just put a blanket prohibition on anything that transmits.



Quoting Nomadd22 (Reply 26):
Airlines have policies to turn pretty much all electronic devices off because

Um isn't this the definition of a blanket prohibition?
Enough about flying lets talk about me!
 
nomadd22
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RE: GPS Coverage In Flight

Mon Aug 25, 2008 11:41 am



Quoting IAirAllie (Reply 28):
Um isn't this the definition of a blanket prohibition?


Try reading the whole sentence. "Anything that transmits" isn't the same as "All electronics devices" I didn't say you could use a blanket prohibition for anything.
Anon
 
bond007
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RE: GPS Coverage In Flight

Mon Aug 25, 2008 1:27 pm



Quoting IAirAllie (Reply 22):
Every US carrier I've worked for specifically prohibited GPS use at all in flight even in cruise.

The rule of thumb is if it sends and/or recieves a signal it is not permitted at all. With a few exceptions.

Actually, quite a few specifically allow handheld GPS devices while in cruise.

Yes, that's the rule of thumb, but handheld GPS is sometimes one of the exceptions (or only in the case of devices that can receive).

Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
iairallie
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RE: GPS Coverage In Flight

Mon Aug 25, 2008 4:55 pm



Quoting Bond007 (Reply 30):
Actually, quite a few specifically allow handheld GPS devices while in cruise.

Yes I am aware that some permit it. However every carrier I'VE worked for has specifically banned them. 6 out of 6 that I worked for did not allow it.

Quoting Nomadd22 (Reply 29):
"Anything that transmits" isn't the same as "All electronics devices"

Your absolutely right. All electronic devices is more restrictive than anything that transmits. A blanket ban on all electronic devices would by default include anything that transmits.
Enough about flying lets talk about me!
 
bond007
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RE: GPS Coverage In Flight

Mon Aug 25, 2008 5:21 pm



Quoting IAirAllie (Reply 31):
However every carrier I'VE worked for has specifically banned them. 6 out of 6 that I worked for did not allow it.

Well, goody for you. Useful to know , I'm sure  Smile

Also remember that this is a fairly new exception for most airlines. In fact AFAIK, the Southwest decision has changed from allowing to disallowing, more than once.


Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
ALexeu
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RE: GPS Coverage In Flight

Mon Aug 25, 2008 10:18 pm

I recently used my personal GPS aboard, and I am very satisfied with it. It gaved me the correct altitude, speed and location.

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