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True GPS or Triangulation on iPhone 4??
- Thread starter JLEW700
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It uses aGPS, which uses to cell towers and wifi networks to narrow down your location and then it uses GPS satellites to find your exact location. This process allows a GPS lock to be acquired faster than standard GPS using only satellites.
And by the way all GPS services of any kind use triangulation to calculate your location. To find an exact point in 3D space (X,Y,Z coordinate plane...Z is used for elevation and X and Y are latitude and longitude) a signal must be acquired from at least 3 satellites (or cell towers or wifi networks) for lat and long and 4 satellites if elevation is calculated as well.
And by the way all GPS services of any kind use triangulation to calculate your location. To find an exact point in 3D space (X,Y,Z coordinate plane...Z is used for elevation and X and Y are latitude and longitude) a signal must be acquired from at least 3 satellites (or cell towers or wifi networks) for lat and long and 4 satellites if elevation is calculated as well.
This is true, and in addition the assisted GPS also allows for the GPS to be used indoors and outside in areas where plain GPS would have difficulty like in urban canyons and heavily leafed woodlands. It is not as accurate as unassisted GPS, but it is usable.
Last week when I was in Chicago and got lost downtown my iPhone said it had a weak signal, but it still kept a good enough track on me that my TomTom navigation app was able to guide me to where I wanted to go.
Last week when I was in Chicago and got lost downtown my iPhone said it had a weak signal, but it still kept a good enough track on me that my TomTom navigation app was able to guide me to where I wanted to go.
Gentlemen, let's be clear, as Apple confused the definition back when the first iPhone had no GPS chip.
Cell tower and WiFi triangulation are not what defines A-GPS, because even without the first two the phone still has A-GPS. They are three separate locating methods, the first two being used when either the GPS isn't ready yet or its accuracy isn't required.
Assisted-GPS in the case of the iPhone means a standalone GPS receiver, with host software that can go on the Internet to almost instantly download current satellite information and thus get a quicker fix, instead of spending twelve or more minutes downloading the orbit info from the satellites themselves.
Cell tower and WiFi triangulation are not what defines A-GPS, because even without the first two the phone still has A-GPS. They are three separate locating methods, the first two being used when either the GPS isn't ready yet or its accuracy isn't required.
Assisted-GPS in the case of the iPhone means a standalone GPS receiver, with host software that can go on the Internet to almost instantly download current satellite information and thus get a quicker fix, instead of spending twelve or more minutes downloading the orbit info from the satellites themselves.
You need 4 satellites to get a proper fix. 3 satellites will give you an exact space co-ordinate on Earth*, and you need the 4th as a 'time keeper' (since GPS systems use time differences to get your position).
(If you want to get technical, you'll actually get 2 distinct points from the 3 satellites, but one of them is either way out in space, or deep underground...)
GPS for IPHONE
Simple answer is YES, however, it is better than most GPS because it has Assist.
I think you are confused because it does not always have maps associated with where you might be, for example, if you are in the wilderness somewhere without cell towers and did not previously download maps for that area nothing will show up in the app...but it will pinpoint your position, but without maps.
Assist, uses the data services to, on the fly, download maps and minimize any GPS gaps due to interference.
In other words, you need to pre-load maps if you think you are going to an area without data services (no cell towers).
Simple answer is YES, however, it is better than most GPS because it has Assist.
I think you are confused because it does not always have maps associated with where you might be, for example, if you are in the wilderness somewhere without cell towers and did not previously download maps for that area nothing will show up in the app...but it will pinpoint your position, but without maps.
Assist, uses the data services to, on the fly, download maps and minimize any GPS gaps due to interference.
In other words, you need to pre-load maps if you think you are going to an area without data services (no cell towers).
If someone wanted to disappear, they shouldn't be carrying along a cell phone in the first place
Speaks volumes of truth. However what others have said, the GPS is assisted in a small way when in the middle of an urban jungle by Wi-Fi and Cell Towers. However, the aGPS meaning comes from what kdarling said.