How does it work...?

[houghw]

Dear all,

First of all, let me apologise if you have touched on this subject before but I was wondering how the hell GPS works on a smart phone...

As far as I understand, my TomTom Go 500 receives data from a number of satellites in orbit and triangulating from that data the unit calculates its position. As far as I know, this is a passive operation, i.e. the Go does not send any data back to the satellites itself and so works independently of them.

Can anyone tell me if this is how GPS in smart phones works? And if so, why do you need to pay a monthly subscription to the service?

I am interested in updating my phone to a model with built in GPS but I’m balking at having to pay a further £5(ish) a month on my contract just to get the GPS to operate.

Thanks in advance...

Wayne

[theripper]

I think you might find that the monthly subscription is for downloading the maps, the GPS works the same way as the TT.
If the phone can run a program like TT Navigator, Copilot, or IGO then there would be no other charges.

[Darren]

GPS is free. Any monthly subscription may be because the app you refer to is delivering map data Over The Air (OTA) rather than from data stored on a memory card.

This has advantages in the the map is always the most current data but it also incurs data fees for each download and solutions that use OTA map delivery use a subscription price model rather than a single up front payment with the application and maps installed to the phone.

Some phones such as Blackberry only offer OTA GPS Nav solutions. Others such as Nokia, Windows Mobile etc have both OTA and traditional onboard solutions.

For a basic GPS primer read my 'How GPS Works' article here.
_________________
Darren Griffin

[robertn]

After years of developing GPS based software and systems, I just got a Sony Ericsson GPS enabled phone. It was a real eye opener for me.

Data Charges -
Theres this thing called "Assisted GPS". I won't go into details, but its a magic way to get a GPS Fix faster. If you turn it off, your GPS will still work, just take a little longer to get a fix. BUT Assited GPS uses data - it costs me 1c each time I use my phones GPS. If you are on a data plan with a minimum data charge, you will get stung the minimum, watch out if you are roam overseas.

Terminology.
When you Sony phone has a GPS fix, SE use the word "Connected" - which is kind of weird way to describe it. The world was happy for 20 years using "Fix" or "2D Fix" or "3D Fix". I think some people see "connected" and think its like a Data conenctions, and get confused.

So although GPS is free, using GPS on you GPS enabled phone may not be.

[JockTamsonsBairn]

[Darren]

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