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9254 clicks; posted to Main » on 14 Jun 2013 at 2:30 PM (3 years ago)   |   Favorite    |   share:    more»

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How will it turn itself off for take-off and landing?
They need a hidden camera in them to film the baggage handlers stealing your stuff.
 1 vote:

threadjackistan: I'm not sure how gps works, range or angle, but if its range(checking the distances in time signal to determine relative distance) and you knew you were on the ground and roughly where you were, the because the potential location of yourself would roughly be a circle from two of the satelites, couldn't you narrow down your location to just two fairly separate points? Again, assuming you were on the ground and had a good DEM.

You're looking at it in a 2D world--that's what you would get if you had two lighthouses honking by a clock and listened to how far away each of them were.  A ship knows the Z and the second point is going to be inland, you have a solution.

However, GPS has to work in a 3D world.  I believe that when you are a variable short in solving such a system of equations you get a line.  That's not going to be too useful.

There's also another problem here--listening to that lighthouse means you must be carrying a clock.  It honked at :00 and you heard it at :04, you knew you were 4 sound-seconds from that lighthouse.  Any *good* clock will suffice as a millisecond error is only about 1 foot.

With GPS, however, the signals are traveling near lightspeed.  (It would be at lightspeed if there were no atmosphere.  The difference matters.)  A millisecond error is 186 miles.  Even a microsecond error is still a thousand feet.  Thus civilian GPS requires an accuracy of say 20 nanoseconds.  Think you can pack a clock of that accuracy in your receiver?  And keep it accurate even when your batteries run out?

Since knowing the time isn't an option you have to calculate it.  We now have four unknowns and that requires four values to figure it out.  Thus you must have a lock on four satellites.  My geometry is rusty but I think one variable short in this case defines a curved surface, not merely a line.  Even less useless than the line.

Note, also, that even with the 4 satellites you still have two possible solutions.  You choose the one on the planet, the other somewhere up near geosync orbit.

Ivo Shandor: GPS devices have an almanac telling them approximately where the satellites are going to be in the sky at any given time. You can see that map regardless of whether or not you're receiving a signal from any of the satellites.

Just a FYI on this--knowing approximately where you are greatly cuts down on the computation needed to lock onto the satellites.
 1 vote:
GPS receivers are one of the things banned from use throughout the whole flight, so how is GPS enabled luggage going to be okay to use?
 1 vote:
GPS Test said the call was coming from inside the house!
 1 vote:

Born_Again_Bavarian: . I put my phone in Airplane mode, turned on the GPS and fired up my GPS tester. I can see 21 satellites.

I can't connect to any, of course

GPS devices have an almanac telling them approximately where the satellites are going to be in the sky at any given time. You can see that map regardless of whether or not you're receiving a signal from any of the satellites.
 1 vote:

Born_Again_Bavarian: StopLurkListen: GPS needs a line-of-sight to the satellite, so unless they drop your luggage off in a field ... good luck

Not necessarily. I sit on the 1st floor of a 3 story building. There are at least 3 walls between me and outside. I put my phone in Airplane mode, turned on the GPS and fired up my GPS tester. I can see 21 satellites.

I can't connect to any, of course but then I don't have any kind of antenna nor is my phone a GPS device first.

I'm a pilot.  With a GPS in a Cessna at 7,000 feet, with nothing to obstruct at all, I can't get that many satellites to lock on.
 1 vote:

Born_Again_Bavarian: StopLurkListen: GPS needs a line-of-sight to the satellite, so unless they drop your luggage off in a field ... good luck

Not necessarily. I sit on the 1st floor of a 3 story building. There are at least 3 walls between me and outside. I put my phone in Airplane mode, turned on the GPS and fired up my GPS tester. I can see 21 satellites.

I can't connect to any, of course but then I don't have any kind of antenna nor is my phone a GPS device first.

Want to know how I know you are lying? There are only 31 GPS satellites in orbit around the entire farking planet.  It'd be pretty damn impressive if your device could somehow connect to 2/3rds of the satellites from a singular location on Earth.

:facepalm:
 1 vote:
Here's a solution, you can fly with as much crap as you can carry, if you can physically lift your bags they go on the plane. Once onboard there are no seats, you sit on your bags.
Then all that spare room we've just opened up by having an empty hold can be put to good use by having a casino down there, or maybe a brothel.
 1 vote:
I'll be able to watch them lose my luggage in real time now.

Sweet.
 1 vote:

StopLurkListen: GPS needs a line-of-sight to the satellite, so unless they drop your luggage off in a field ... good luck

Please tell me you're trolling.  My iphone can tell which room of my house I'm sitting in.
 1 vote:
As neat as this is, it has one major flaw: it relies on anyone at the airport giving a fark about your missing bag.
 1 vote:

Delta Baggage Handler

 1 vote:
GPS needs a line-of-sight to the satellite, so unless they drop your luggage off in a field ... good luck

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