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  1. jrv
    jrv is offline
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    Originally posted by AJB
    Yes it does. The snap track AGPS has the location calculated by the network. No network, no location.

    Network -> provides coarse location to handset AGPS chip
    Handset -> locks & listens to GPS satellites
    Handset -> provides location centre with GPS data
    Location Centre (network) -> calculates location.
    Location Centre (network) -> may provide data back to handset or to requesting network based service.

    No network, no GPS position, because[list=1][*]no initial location to get satellite bearings (this could mean a search of > 1 day just to get satellite info), [*]No location centre to do the grunt work of calculating the position from the GPS receiver. This is also computationally expensive.[/list=1]
    It might be better to say “No network, no quick location”. If the phone is capable of downloading the GPS almanac then it could do satellite selections & the calculations itself.

    If the AGPS chip can’t make almanac information from the satellite broadcasts available then no position calculation is possible in the phone. The only possibility then is to have the phone retrieve an almanac over the internet, which requires network availability and a site somewhere that keeps a current almanac in a useful form.

    The calculations for GPS may have required a lot of CPU back when GPS was developed but CPUs are much faster now. I’d bet that the Treo CPU is a lot faster than most GPS units. I think the timing requirements, to measure the small delays between mark pulses from the satellites, is much harder to do.

    The question I’d have is battery life. A Treo app could cache an almanac in memory, but if that is stale and a new one needed then the phone must stay awake and listen. It might be cheaper in terms of battery life to download the almanac over the Internet in this case. After that you need to collect several samples to get the error circle down, and that may take time if you’re moving erratically as samples are being collected.

    The almanac is broadcast by the satellites every 15 minutes. There’s no need to wait a day.

    One of my older phones, either the Kyocera QCP-6035 or Treo-300, had a debug page that gave the geographic coordinates of the tower you use were using. This provides good enough information, along with a current almanac, to do a rough location estimate quickly.
  2. #22  
    If this data is usable it could be interesting. Even if it is just the location of the tower.

    Take a look at this program for Symbian P800 - miniGPS -- for an example of what could be done.
  3. #23  
    SnapTrack is the system and is owned by QUalcomm of CDMA fame. This was described accurately above. But why adopt this and not just put a real gps chip in the phone?

    Reason 1 is that if the carrier does it, then no matter the CPU power of the phone, lat/long calculations can be made for any user
    Reason 2 is that this system was already available and was the only choice to meet world governments insistence on geopositiong info for a cell phone (for ermergency and homeland security reasons)
    REason 3-----the secret---- Since you don't kknow where you are and the Carrier now does, they control you and can offer this control to avid marketers. Scenario----You are cruising on Interstate 999 at lunch time. Your phone location is interpolated by Sprint in a separate computer system. They send you a SMS that says there is a Mickie D's ten miles ahead.---and would you like driving instructions, turn by turn. Also would you like a super size coupon on a Big Mac? Of course you would and it is now in your phone. Following the directions on your phone, you pull in to Mickie Ds and drive up to the window. You beam the T600 at the order window and your order is lowered down to you and the coupon for the big mac is IR beamed and credited to your account!

    Not so bad and Sprint dings McDonalds for the comarketing charge. In this scenario, the local cardioligist now knowing you love the fat offers you a buy one, get one stent for your clogged arteries-----along with driving instructions to his clinic. The local hospital hearing from the system that you are going to the cardioligist, sends you a SMS offering turn by turn directions to the ER..............
    So you can see where this is all going...... And the carrier controls the whole mess....... This is why they can't wait to get sufficient mass of capable phones out there.........
  4. AJB
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    Originally posted by jhaglund
    REason 3-----the secret---- Since you don't kknow where you are and the Carrier now does, they control you and can offer this control to avid marketers...
    This is why they can't wait to get sufficient mass of capable phones out there

    Q: How do you make God laugh?
    A: Tell Him your plans :-)
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