re: Official Thread: Missing Malaysia Airlines Flight 370

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"Bout to board the plane, got my new Jordan Shoe Bombers on... Wish me luck"

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True, but what are thinking you will find? I doubt anyone had any reason to suspect anything. And I doubt anyone involved is gonna tweet.... "Bout to board the plane, got my new Jordan Shoe Bombers on... Wish me luck"

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One of the Iranians posted this on his facebook LINK

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How about this, cell phone related...

Pilots work on turning off transponders, etc right after leaving Malaysian air space. Put on oxygen masks. then do some procedures that pressurized the cabin, which takes oxygen out which takes out most of the passengers. After that cluster is over, there would be no reason to expect dead passengers to make calls/posts online.

Just basically saying, you do something that kills everyone and most problems solved

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Cell Phones don't work at 30,000 feet 200 miles from the closest cell tower. They just don't work without a signal from a tower and the signals can only travel so far.

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GPS, the Global Positioning System run by the United States Military, is free for civilian use, though the reality is that we're paying for it with tax dollars.

However, GPS on cell phones is a bit more murky. In general, it won't cost you anything to turn on the GPS in your cell phone, but when you get a location it usually involves the cell phone company in order to get it quickly with little signal, as well as get a location when the satellites aren't visible (since the gov't requires a fix even if the satellites aren't visible for emergency 911 purposes). It uses up some cellular bandwidth. This also means that for phones without a regular GPS receiver, you cannot use the GPS at all if you don't have cell phone service.

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For this reason most cell phone companies have the GPS in the phone turned off except for emergency calls and for services they sell you (such as directions).

This particular kind of GPS is called assisted GPS (AGPS), and there are several levels of assistance used.

GPS

A normal GPS receiver listens to a particular frequency for radio signals. Satellites send time coded messages at this frequency. Each satellite has an atomic clock, and sends the current exact time as well.

The GPS receiver figures out which satellites it can hear, and then starts gathering those messages. The messages include time, current satellite positions, and a few other bits of information. The message stream is slow - this is to save power, and also because all the satellites transmit on the same frequency and they're easier to pick out if they go slow. Because of this, and the amount of information needed to operate well, it can take 30-60 seconds to get a location on a regular GPS.

When it knows the position and time code of at least 3 satellites, a GPS receiver can assume it's on the earth's surface and get a good reading. 4 satellites are needed if you aren't on the ground and you want altitude as well.

AGPS

As you saw above, it can take a long time to get a position fix with a normal GPS. There are ways to speed this up, but unless you're carrying an atomic clock with you all the time, or leave the GPS on all the time, then there's always going to be a delay of between 5-60 seconds before you get a location.

In order to save cost, most cell phones share the GPS receiver components with the cellular components, and you can't get a fix and talk at the same time. People don't like that (especially when there's an emergency) so the lowest form of GPS does the following:

Get some information from the cell phone company to feed to the GPS receiver - some of this is gross positioning information based on what cellular towers can 'hear' your phone, so by this time they already phone your location to within a city block or so.
Switch from cellular to GPS receiver for 0.1 second (or some small, practically unoticable period of time) and collect the raw GPS data (no processing on the phone).
Switch back to the phone mode, and send the raw data to the phone company
The phone company processes that data (acts as an offline GPS receiver) and send the location back to your phone.
This saves a lot of money on the phone design, but it has a heavy load on cellular bandwidth, and with a lot of requests coming it requires a lot of fast servers. Still, overall it can be cheaper and faster to implement. They are reluctant, however, to release GPS based features on these phones due to this load - so you won't see turn by turn navigation here.

More recent designs include a full GPS chip. They still get data from the phone company - such as current location based on tower positioning, and current satellite locations - this provides sub 1 second fix times. This information is only needed once, and the GPS can keep track of everything after that with very little power. If the cellular network is unavailable, then they can still get a fix after awhile. If the GPS satellites aren't visible to the receiver, then they can still get a rough fix from the cellular towers.

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In the higher end phones with a full GPS receiver you may even be able to load your own software and access it, such as with mologogo on a motorola iDen phone - the J2ME development kit is free, and the phone is only $40 (prepaid phone with $5 credit). Unlimited internet is about $10 a month, so for $40 to start and $10 a month you can get an internet tracking system. (Prices circa August 2008)

It's only going to get cheaper and more full featured from here on out...

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