Why isn't my cell phone a bluetooth GPS

Submitted by brad on Sun, 2006-04-02 12:17
Topic: 
Technology
Telecom

GPS receivers with bluetooth are growing in popularity, and it makes sense. I want my digital camera to have bluetooth as well so it can record where each picture is taken.

But as I was drivng from the airport last night, I realized that my cell phone has location awareness in it (for dialing 911 and location aware apps) and my laptop has bluetooth in it, and mapping software if connected to a GPS -- so why couldn't my cell phone be talking to my laptop to give it my location for the mapping software? Or ideed, why won't it tell a digital camera that info as well?

Are people making cell phones that can be told to transmit their position to a local device that wants such data?

Update: My Sprint Mogul, whose GPS is enabled by the latest firmware update, is able to act as a bluetooth GPS using a free GPS2Blue program.

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Comments

Kieran

Sun, 2006-04-02 14:38

Brad;

This reminds me of the questions that came to mind when I was given a Palm Treo cell-phone last Christmas, and I saw that it had some sort of a GPS receiver in it. Goodie! Free GPS along with the Treo!

Sadly, not so simple (*). My Treo (and, I suspect, most cell-phones) use "Aided-GPS" technology to fulfill the mandated E-911 requirement. I found a few decent explanations on the web of how this works, e.g., at http://www.sirf.com/downloads/collateral/Press_Releases/BeyondAGPS.PDF.
Basically, the cell-phone contains only partial GPS functionality (reading raw GPS signals), with the computation of your location done by computers in the cellular network (taking advantage of the rough location knowledge provided by the knowledge of which cell you're in, to speed the solution).

So, your cell-phone doesn't quite have location awareness; instead, it has to ask the network to tell it where it is. Generally, except for 911 situations, the network operator doesn't give you that for free; I gather that there are a number of Aided-GPS subscription-based services that are either already available, or about to be made available, to cell-phone subscribers.

Once you subscribe to one of those services, then the application that you suggest (bluetooth link to laptop-basde mapping software) would be eminently feasible, I think. (It would require the purveyor of the cell-phone software application to make the location data available to other programs on the cell-phone, and/or to provide you with a driver to pass that along to your laptop, or somethnig like that---i.e., they'd have to be cooperative with whoever wanted to deliver the laptop-based interface software).

That being said, I believe that some of the services to be offered include similar functionality, but entirely on the cell phone.

(*) Looks like I get what I wanted via another route---Bell Mobility is giving away free add-on Palm GPS receivers with bluetooth, that will talk to my Treo, to those of us who have bought certain of their wireless plans; this includes Tom-Tom mapping software for the Treo. Mine should be in the mail---looking forward to it! AFAIK, this does *not* use the Aided-GPS feature of the Treo; the Palm GPS receiver appears to be a non-aided stand-alone receiver.

brad

Sun, 2006-04-02 20:06

Perhaps in error, that the aided GPS (in CMDA phones like Bell mobility /Telus) and Verizon/Sprint was somethting to be better than ordinary GPS, because it could use signals from cell towers as well as satellites, and thus pick them up inside buildings more easily and get an even more accurate reading. Sad to see it is in the tower not the phone in many of these cases. Another case of the great tragedy that comes from cell phones being designed to please carriers, rather than users.

Though I have two GPS receivers already, it is indeed a pain to manage all the cables to power them and get data from them. There are two options. Bluetooth of course is nice and wireless, and hopefully in the future will be able to talk to my digital camera. But the GPS, in the car at least, will still need a power cable or a frequent change of battery. The USB GPSs that Delorme sells also seem nice -- a cable, but it does both data and power. The other plus of this is that many cars these days cut off power to the 12v jack when turned off or even for a second when turning the key. That screws up an external powered GPS whose battery has died, it's really, really annoying. (I do wish cars came with a switch so you could control if the 12v jacks would be always-on or only on when other accessories are.)

Anyway, the USB powered GPS by taking power from the computer gets power as long as the computer is on, which is fine. Sadly digital cameras are being pretty slow to support bluetooth or bluetooth GPS. However, as noted, another solution is to, after copying the photos to the laptop, have it suck down the GPS track log from the bluetooth GPS, and write the latitude and longitude into each picture for you.

Kieran

Wed, 2006-04-05 13:31

Brad;

I think what you were told was not in error; I have also seen (read in a couple of technical papers) the claim that aided GPS provides better performance in low-signal situations (e.g., inside buildings). I gather the reason is that knowing which cell tower you're talking to tells you where you are to within a few km, so the software used to estimate your position from the GPS saetllite signals doesn't have to search through as wide a parameter space (i.e., doesn't have to search all possible locations on Earth), and so can spend more time doing correlations for each candidate location, and hence can achieve an adequate signal-to-noise ratio per correlation even in low-signal situations. (That's probably an over-simplified explanation, but I think it correlates well with an accurate one :-)

As for Bluetooth GPS receivers, check out the new one that Palm is selling for CDN$350:

http://canadastore.palm.com/product/index.jsp?productId=2041928&cp=1157581.1263670

(This is the one that I'm hoping to get soon from Bell Mobility.) They have aimed this to interface with their various PDA/cell phone products; I don't know if they sell driver software that would run on a laptop computer to talk to this. However, perhaps the communications protocol for this might be available, allowing you to write your own driver?

brad

Thu, 2006-04-06 19:30

Bluetooth GPS are much cheaper than that -- I see Froogle listings down to $75, so I guess the software is part of what you're paying.

Indeed, it does seem that it would make a lot of sense to offer a stripped down bluetooth gps that just receives the signals and transmits them to the computer, which does the hard work, though I guess you want to know a bit about where you are to figure which satellites to listen to? I presume that would not make it easy to just transmit the raw data to a camera when it requests it (on picture take) so the camera can store the raw data in the photo file and the software later can convert that to location.

But a PDA or laptop could certainly handle these things. (Actually the camera CPUs are pretty good too.)

Just trying to carry fewer devices. And not pay locked-walled-garden fees for basic things, like receiving GPS. Actually, since most cars will have GPS before long, it seems they could also have bluetooth so that if your camera doesn't have GPS, then when you return to your car it can at least store where your car was for the pictures. So you wouldn't get a map of exactly where on the grand canyon rim you shot the photo, but you would know it was shot at the grand canyon.

Aleks Totic

Mon, 2006-04-03 16:36

The reason that cell phones do not do full GPS is battery life. Doing full GPS in phone drained batteries fast. Data transmission was easy on the power, someone clever put it all together & patented the idea. The phone companies tried to come up with an alternative to avoid patent costs, but without success.

You could transmit raw GPS data to your portable, and have it to do the math.

Aleks

brad

Tue, 2006-04-04 06:19

In car, one could have the phone plugged in and not worry about power. For cameras, the camera could query the GPS location only when taking a picture, and that wouldn't use as much power. However, it would have been nice to not have to plug in the phone to track your car.

Aleks Totic

Fri, 2006-04-07 14:57

Looks like processing raw GPS data is not that complicated (there are SDKs on the web). I guess that the battery drain comes from continuous usage. When taking pictures, the phone could calculate the real GPS location when picture is taken. I am sure that the act of taking the picture is more power intensive than the GPS calculation.

This is not being done yet probably because the marketing cut the feature out as too obscure. You could easily write a little app that would do what you want.

Brandon

Thu, 2006-08-31 15:52

I've written code in Matlab to take raw pseudoranges from each satelite and produce an adjusted (and atmosphereic delay corrected)location Good to ~+/- 10m (I assume the phone doesn;t support Wide-Area Augmentation System or any other Differential corrections. Its really not that complicated given knowledge of GPS/how it works/etc. Running the softwre would be WAYYY less computationally intensive than say playing tetris, or any other graphical phone game.

I personally have no idea how to access the GPS data in the phone at the software level (is there an SDK?), I have no idea how to even get software ONTO the phone, Nor have I written code for a phone before, but I do know Java quite well.

If the decoded pseudo-ranges are determined in the phone, which they would have to be by my guess, unless the phone literally relays everything it reads (as raw binary information) back to the network (which is also possible) Then it is DEFINITELY doable. Even then, if that information can be accessed on demand (which is must be as it is only sent when requested by the carrier) it can be decoded, and used to determine ones location relatively easily. Expect accuracies in the range of 10-20 metres, precision 5-10 metres at best.

If there is anyone that is willing to work on this, and wants help on the GPS processing side of things I can probably help out (as opposed to the "making it run in a phone bit", which I know nothing about).

you can email me at:

01100010 01110010 01100001 01101110 01100100 01101111 01101110 00101110 01101101 01101111 01101100 01000000 01100111 01101101 01100001 01101001 01101100 00101110 01100011 01101111 01101101

(ASCII-->binary. What better way to keep spiders from getting it?)

By the way, I have an engineering degree in Geodesy and Geomatics engineering.

mike

Fri, 2007-02-23 22:13

Well, if you have written a java app that could be handy to start out with. There are some field service settings in my samsung a900/a920 that when accessed, have some info that appears to be GPS info. I am not quite sure about it thought. the words have GPS in them, but the data it reports looks strange. Perhaps this is the "raw" data, but I dont know what raw gps data looks like.

mike

Fri, 2007-02-23 22:14

contact me at mikewattersAThotmailDOTcom

Peter Rowley

Mon, 2007-08-27 20:47

Hi Brad,

The smallest GPS made for capturing positions that are later merged into the EXIF information in digital camera pictures that I've seen is from Sony: http://www.sonystyle.ca/commerce/servlet/ProductDetailDisplay?storeId=10001&catalogId=10001&langId=-1&productId=1003212

But at CDN$129, it's not a lot more to get a real GPS receiver with a good display that will record a track to a microSD card and can actually have longer battery life than the Sony unit (e.g. 32 hours for the Garmin eTrex Vista cx). Though the Garmin unit is considerably bigger.

Peter

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