How fast is your airplane?
I have to wonder if the cabin crew would be happy with this, but it’s still amazing that you can actually do it. Over at the E-Series blog, they used a Nokia E61i with a GPS receiver to figure out airspeed while on a flight. Makes sense that it would work since the plane had be lower than the GPS satellites; their geosynchronous orbits are around 26,600 miles out. Using the Tom-Tom software on the E61i it was easy to see that the plane was moving at 777 kmph. Sweet and now I can cross off geosynchronous from my "difficult words to use in a blog post" bingo card.
GPS Satellites are not in geosync orbit, but are actually at around 12,600 miles. And even the Space Shuttle is now equipped with GPS to assist with navigation, since it’s typically only a few hundred miles up.
But yea, it’s is kinda cool seeing such a speed in a handheld GPS.
Thanks MikeB! My bad…will edit to reflect the correction. You’re correct on the altitude; my number came from the orbital radius of 26,600 km (not miles…so I goofed on that too!)
http://www.panoramio.com/photo/2958691
This fast! Did it a while ago whilst on the way back from Barcelona, BT GPS and LifeDrive.
NB: mine was slower as we were coming out of the LHR stack.
Use of a GPS receiver at any time on a commercial flight is illegal.
Many folks consider the cellphone ban a conspiracy for the airlines to make more money. Whatever.
But I’d feel really bad if some passengers GPS was defective, interfered with the planes GPS and we wound up at risk over it. That kind of thing can ruin the rest of your life.
I am curious as to why you feel the GPS satellites have to be “above” the observer to get a position fix? GPS satellites are used to create position fixes in much the same way as the stars, except unlike stars they are available 24 hours a day. There is no technical reason why GPS couldn’t be used from say the L5 point (although I’m pretty sure a $100 Garmin would be horribly confused.)
The big fear on airplanes is that a portable electronic device will emit electromagnetic radiation (radio waves, mostly) that interfere with the airplane. But GPS is a receive-only application, it uses a receiver without needing any sort of transmitter. The GPS radio signals are already in the air, and are clearly not causing problems with existing aircraft electronics. About the worst thing a GPS could do is give you the wrong location, without a transmitter of some sort they essentially can’t interfere with other devices. They might be illegal for passengers to use on commercial aircraft, but there’s no good reason for it.
And yes, you can get a location from GPS if you are above them, at least in principle. I wouldn’t try from the L5 point, since you’d be too far away from the satellites to get any sort of accuracy.
Actually the rules for GPS use vary from carrier to carrier. Check out: http://gpsinformation.net/airgps/airgps.htm
I’ve used a GPS receiver on some flights with great success. I didn’t have a SIRf III device, I was using a Garmin Rino, so the signal was a little week and I had to suspend the receiver in the center of the window, but I was able to track the course. What’s more, after I had saved those airports as markers, I had ETAs and headings at my disposal too. A nice aspect of a full featured GPS unit and not a car navigation unit.
Kevin, the 777 figure is acutually showing the ground speed not the “air speed”. Meaning the plane was traveling over the ground at 777 kmph, not that the air was wooshing by the plane at 777 kmph.
Airspeed is calculated by figuing out how quickly the surrounding air travels by the airplane. Ground speed is decreased by a head wind and increased with a tailwind. Just wanted to clarify and is cool none-the-less!!
“Use of a GPS receiver at any time on a commercial flight is illegal.”
That is incorrect, at least here in the US. In fact, on one of the last flights I was on (maybe JetBlue or United), the magazine even indicated GPS is an “approved” electronic device. You will scare the crap out of the people around you who assume the worst and you’ll need to sit in a Window seat to get a signal, but it’s fun to see where you are and how fast you’re moving.
If you’re above the satellites, you may still be able to get a fix, but it would likely be considered bogus data once you doubled your radius past the center of the Earth, if not earlier.
For one, the higher up you go, the more birds you can “see.” At a certain point, you’ll get signals from over half of the GPS satellites, and while that’s not necessarily a *bad* thing, it’s going to probably confuse the hell out of receiver unit.
Since it’s all based on triangulation and clock signals, though, I’m pretty sure that you’d get an accurate latitude, longitude, and elevation to somewhere around 25,000 miles up, provided you were just sticking to the raw math. How much of that is distorted by background radiation and the lack of atmosphere is an exercise best left for someone who isn’t idly speculating.