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combatdoc is offline combatdoc
2008-06-17 , 00:07
Posts: 204 | Thanked: 29 times | Joined on May 2008
#31
Originally Posted by bunanson View Post
To Tabletrat and Geneven: I stand corrected. I agree, in general, GPS should work under most altitude, mine is not, dont know why. And as other people has put it, theirs work in USA/Europe/Asia. Mine does not work in Asia at all. But now I am back in USA, the BT GPS works like a charm. Does GPS has to log with a 'particular' satellite, or any satellite, with tirlaterization will do? witch crafts!

bun
I know that on my garmin I had to go into the settings and change the region so it would read GPS over the Middle East, otherwise it just kept trying to find GPS Satellites over the US. I didn't see any way to do that with the n810 though.
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mullf is offline mullf
2008-06-17 , 02:28
Posts: 610 | Thanked: 391 times | Joined on Feb 2006 @ DC, USA
#32
Originally Posted by bunanson View Post
My gps does NOT work most of the time during flight, except on landing and take off. because of the altitude of the flight? Mine is transatlantic flight, presumably much higher than domestic flight, I guess?
Not the height. You are actually closer to the satellites up there. But consumer GPS receivers will not give a position if they detect you are going above a certain speed. The idea is to not let them be used as part of a guidance system for some type of missile.
 

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mullf is offline mullf
2008-06-17 , 02:30
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#33
Originally Posted by bunanson View Post
More info here, Airlines which OFFICIALLY APPROVE the use of GPS receivers during CRUISE.
That's right, RECEIVERS. Bluetooth GPS units are also TRANSMITTERS, and are not allowed.
 

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mullf is offline mullf
2008-06-17 , 02:34
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#34
Originally Posted by tabletrat View Post
the plane you are sitting in has a fully functional GPS system, so why would it not work?
I'm not sure, but they may be specialized not to have the threshold consumer GPSs do, or to have a higher one. Or, probably more likely, you do travel fast enough on a plane to hit the threshold for either, and the one gentleman's receiver is just idiosyncratic.
 
DJames1 is offline DJames1
2008-06-17 , 18:21
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#35
I've used my handheld Mio GPS during flight (GPS is receive-only, so allowed during flight). It works ok as long as I'm in a window seat. Further inside the aircraft you're basically inside a Faraday cage = no signal. It's really cool to capture a 3D track and then plot the 3D flight path in Google Earth.

I've seen various people theorize previously that airspeed or altitude might be the explanation for failure to get a position fix, but neither of those are true - it's just satellites in view and signal strength.

Technically you aren't allowed to use Bluetooth devices during commercial flights since they transmit, and you aren't allowed to use any electronic devices during takeoff/landing. In reality both restrictions are probably overly cautious. Researchers testing and recording the cabin RF environment on commercial flights report that virtually every airline flight has at least several people who have forgotten to turn off their cell phones and/or WiFi devices. However I wouldn't recommend violating airline restrictions, or might get you kicked off a flight - you might as well argue that your 125ml toothpaste tube is not a dangerous explosive. :-)
 

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GeneralAntilles is offline GeneralAntilles
2008-06-17 , 18:38
Posts: 5,478 | Thanked: 5,222 times | Joined on Jan 2006 @ St. Petersburg, FL
#36
Originally Posted by mullf View Post
Not the height. You are actually closer to the satellites up there. But consumer GPS receivers will not give a position if they detect you are going above a certain speed. The idea is to not let them be used as part of a guidance system for some type of missile.
Correct, I'm not sure what the threshold here is, though. I know I've gotten a lock at around 550MPH with my i-Blue 737 more than once, though.

With most consumer GPS units the issue will be one of velocity, not necessarily because of internal locks, but because the receivers have a hard time getting lock at higher speeds.
 
DJames1 is offline DJames1
2008-06-17 , 18:56
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#37
Originally Posted by GeneralAntilles View Post
With most consumer GPS units the issue will be one of velocity, not necessarily because of internal locks, but because the receivers have a hard time getting lock at higher speeds.
Sounds plausible, but not really. The position fixing firmware is all built into the GPS chipset - probably one of the same chipsets that's used in airborne GPS receivers. Wouldn't be much use if it couldn't get a fix at normal flight speeds, would it? I normally have to hold mine up to the window to get an initial fix in a reasonable amount of time, but after that it's good. Doesn't make any difference if the aircraft is sitting at the gate or in flight at full speed.
 
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GeneralAntilles is offline GeneralAntilles
2008-06-17 , 18:57
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#38
Originally Posted by DJames1 View Post
Sounds plausible, but not really. The position fixing firmware is all built into the GPS chipset - probably one of the same chipsets that's used in airborne GPS receivers. Wouldn't be much use if it couldn't get a fix at normal flight speeds, would it?
No, aircraft don't use consumer GPS chips. :\

Moving has an effect on the position of the satellites relative to you and complicates the locking calculations, resulting in longer lock times.
 
DJames1 is offline DJames1
2008-06-17 , 19:35
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#39
Originally Posted by GeneralAntilles View Post
No, aircraft don't use consumer GPS chips. :\
Might once have been true, but no longer. Google "aeronautical" and "SiRFStar III". Convergence.

Moving has an effect on the position of the satellites relative to you and complicates the locking calculations, resulting in longer lock times.
Theoretically true, but the effect is not very significant with modern GPS chipsets, and hard to separate from the effect of being inside a metal box (car or plane).
 
XM40 is offline XM40
2008-06-18 , 15:35
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#40
Let's remember, the airlines were about to allow cellphone calls during flights. They would have to install a cell tower, so to speak, in each aircraft to pick up your signal and transmit down to the earth towers. They were going to charge ~$1.00/minute. There was such a hue and cry from the public not to allow this, that for the time being it is a dead issue. So, the airline knows that there is no problem (European airlines do allow cellphones) with cellphones when there is a profit to be made. So if in fact cellphones are safe during flight, then gps is definately safe.
 
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