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Using the GPS Features of Your Cell Phone?
travik asks: "I use a Nokia 3650. The cell phone already knows my co-ordinates (E911 service). It has Bluetooth. Why can't I send the coordinates using Bluetooth to my laptop, and use a mapping application to give me my location and directions to where i want to go. I've searched Google and also read up on old posts, no one seems to be doing it. Why?"
E911 lets the service provider know where you are by your tower connection (and perhaps by other tower signal strengths). It's expensive to keep track of, but is required by law. They don't have enough financial interest in returning that location information to you yet.
AGPS (assisted GPS) also depends on the service provider to calculate your location, but it actually uses real GPS satellite signals to do it. The signal strengths are uploaded to a server which does the heavy-lifting of figuring out the location. Again, this depends on the SP servers and they aren't going to be terribly interested in returning lots of location points back to you.
Real GPS does the CPU work on the device. There are rumored to be a few phones with this capability, but I use a Garmin Gecko 301. $228, records 10K points, downloads via serial port (yuck), and burns a set of alkaline batteries in 7 hours (or less). IMHO, it'll be a while before location information is as easy to get to as the cheapest GPS. Battery power is just too valuable.
This guy tracks his location by phone.
Where is Calum?
Cheers,
Roger
Do you have any better hostages?
I'm currently working on my PhD project involving location based services. From my research, I've discovered that a much more accurate location estimate is possible than the simple "strongest cell tower". Basically you meassure the signal strengths from all available towers (or access points), and do some calculations based on this information. Finally you find the best match in a database of location/signal-strengths, and interpolate a position.
/Spiff
I first saw this technology used on WLAN. Ehahau uses this technology to provide location based services on WLAN, and it works great. In our test setup at the university, we get arround 1 meter error in the position.
I've been in touch with a group of people at The IT-University of Denmark, who are working on using this technology on GSM cellphones. The biggest problem here is getting access to the data. The cellphone companies simply do not want to provide this information. Our collaborative guess was that they want to keep this information to themselves, probably to sell extra services.
The main drawback of this technology is that a huge amount of calibration is needed to make it work. On WLAN our buildings have been calibrated in a grid of 3x3 meters, which makes quite a lot of calibration points when we want coverage of the entire campus. But the cool thing about it is that it does not require any extra hardware to do the localization. A labtop or PDA with wireless will do the job.
You can download the location of ~all cell towers from the FCC
http://wireless.fcc.gov/geographic/fcc_db.html
(big files) as they are publically licensed, but you can't know the carrier's private ID # of the tower without matching the tower's license to what you phone tells you, as some do.
The first test launch of a stand-alone GPS phone is several quarters away... The CDMA chips are basically capable, but need some extra hardware and firmware since they don't get a kick-start from the tower/server communication.
Right now, if your carrier doesn't have the PUBLIC servers installed (they will not use their e-911 servers for commercial use for liability reasons) then you can't have GPS.
And BTW, the carrier's servers do know your location because of the MS-* handshaking and communication (which allows the ephemeris calculations to be done faster on your phone), it's a question of whether it gets saved or tapped.
It's---a-small-world-after----all---...
Sigs are for propeller heads.