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GPS is too slow for a lot of location based services.

two cell sites on a single mast

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A lot of folks have high hopes for the new location services with GPS coming on iPhone 3G. I’m reserving judgement. Having been a GPS user for some time, including using phone based GPS on various Nokia devices and the Blackberry 8310, I’m just not that excited.

The most exciting location tool I’ve seen in a long long time was the simple tower triangulation that was done in iPhone 1.0. Why? Because it was fast enough. Yes, it wasn’t accurate. But it was fast enough to instantly show me the location of the nearest starbucks, for example. GPS just isn’t that fast. Moreover, I don’t need 3m of precision to find a coffee shop and I don’t have the patience to wait a minute or more for the GPS fix.

So here’s a modest proposal. Why not progressively render location? Give me the near instantaneous cell tower fix when I start a location consuming app. Then, while I’m using the application, acquire the satellite fixes in the background and present me with better precision data if I want it.

GPS is perfect for navigation. But if you just want an instantaneous locate, it’s probably overkill for many applications.

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{ 12 comments… add one }

  • Martin Dufort June 11, 2008, 5:58 am

    Alec:

    With the inclusion of A-GPS in the iPhone 3G, you are right, the dream of more ubiquitous location-based services are getting closer to reality.

    As for your progressive location discovery, there is no reason why this could not be implemented by Apple in their Core Location API. We still have to investigate it but your point is a good one.

    To find the nearest Starbucks, WIFI-Cell tower trilateration is good enough. For geocaching and using you phone in rural area to turn-by-turn directions, the precision is really not good enough.

    I think Apple's solution is overcoming this limitation by including both.

    Happy location reporting – Martin

  • David Megginson June 11, 2008, 8:34 am

    GPS is actually very fast once it has acquired its satellites — it can update your position several times each second (it's good enough, for example, that airliners can use it for guidance to the runway in low visibility). The trick is that the GPS has to be on and *stay* on (e.g. you turn it on when you leave the house in the morning) — that creates a conflict for battery powered devices like cell phones, which you want to leave on standby until you're actually ready to make a call. I'm not sure how much power the GPS would consume if it kept running when your phone was closed.

    The other problem in urban environments is that tall buildings make it difficult for the GPS to see enough satellites.

  • Pej Roshan June 11, 2008, 8:45 am

    Hi Alec-

    I agree. Our company, Agito Networks, uses location as a metric for handing over mobile calls between WiFi and cellular. We evaluated a number of techniques to determine location, including GPS, and found the fastest means was via WiFi and cellular measurements. Along the lines of your notion of progressive location, we agree. There is likely no silver bullet for location, rather combined metrics.

    Here is a video blog post we did a few months ago on the topic
    http://www.agitonetworks.com/blog/?p=16

    Pej

  • Brad Templeton June 11, 2008, 9:57 am

    Actually, it should be possible to make a very fast GPS if you already know the approximate location from the cell towers. Perhaps even faster if the cell towers were to tell you which GPS satellites are the ones to listen for at this moment. And super-duper accurate to a foot if the cell towers were to also tell you clock corrections for the local area.

  • matt roberts June 11, 2008, 10:10 am

    Brad,

    Similar technology was developed in Canada by a company called Cell-Loc which did both triangulation from the cell towers to give location to both carriers for asset tracking and down to the phone for assisted GPS mobile acquisition. From what i gather it never really caught on.

    mr

  • Alec June 11, 2008, 10:52 am

    That's interesting information Brad and Matt. So it's *simply* a matter of convincing carriers to upgrade towers?

  • Brad Templeton June 11, 2008, 6:47 pm

    I am not sure you have to upgrade towers too much to make it fast. There are some aGPS phones that already do this.

    The trick is, for a GPS to get a fix, it needs an up to date ephemeris for the satellites. These last only 4 hours so you need to constantly update them. Which you can do from the satellites but first you have to find them and wait for them to send it etc. If you can pick up your ephemeris and almanac over the cellular network, you can dig right in to decoding signals from satellites. And you don't need as strong a signal.

    In addition, local towers can tell you the current locally induced error for your area, letting you be very accurate.

  • Jim Courtney June 13, 2008, 6:22 pm

    My experience with the most recent version of Google Maps on a Blacbkerry 8820 or a Nokia N95, which has A-GPS (A=assisted by cell tower) is that it locates the nearest cell tower quite quickly and after a few minutes will narrow in once it has the satellites alignment. It is the nature of GPS receiver chips to take a bit of time to get going once turned on. Once they have a location they are quire useful even to tell you the speed at which you are traveling as well as direction changes, etc.

  • Jim Courtney June 13, 2008, 6:23 pm

    My experience with the most recent version of Google Maps on a Blacbkerry 8820 or a Nokia N95, both of which have A-GPS (A=assisted by cell tower) is that it locates the nearest cell tower quite quickly and after a few minutes will narrow in once it has the satellites alignment. It is the nature of GPS receiver chips to take a bit of time to get going once turned on. Once they have a location they are quire useful even to tell you the speed at which you are traveling as well as direction changes, etc.

  • gps vehicle tracking October 27, 2009, 7:01 am

    Excellent site and educational posts, Could I ask if GSM or GPS trackers are best?

  • GPS Navigationssyste January 28, 2010, 4:59 pm

    Garmin sells an excellent devices regarding the hard and firmware. They have a better quality products and more user friendly.

  • Kai Collins May 27, 2010, 4:26 pm

    GPS is very useful specially the ones that are put on the Car dashboard. it can really help you drive on unfamiliar places.-*~

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