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Apple Mobile Products: iPhone, iPad, iPod
iPhone Hardware and Accessories
The downside of buying a used iPhone
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<blockquote data-quote="MacInWin" data-source="post: 1827436" data-attributes="member: 396914"><p>One more thing: The way that the cell service does the most to speed up the GPS fix is that your cell phone can get the almanac data faster over cell using a bit of your data allowance so that as soon as it has ephemeris data from 4 satellites, you have a fix. Normally that's in less than a minute, which can be disguised in the start up routine for the GPS application on the phone. To you, it looks practically instantaneous, but a lot of stuff is going on in the background to make it happen.</p><p></p><p>EDIT: One more one more thing. GPS (or SatNav) will be showing where you WERE, usually about a second ago, as it takes some time for the signals to arrive, the fix to be calculated and the map updated. The navigation software anticipates that delay and forecasts where you SHOULD BE based on speed and direction you travelled a second ago. Normally, that forecast is correct, but sometimes it's not. If you are directed to take a turn and do not do so, it takes a second before the GPS fix shows you not there, and two fixes to figure out what direction/speed you did travel. So the map software assumes you took the turn, projects where you SHOULD BE if you did turn and has to correct when it figures out you didn't turn. That delay is why you see the map jump a bit at turns you ignore.</p></blockquote><p></p>
[QUOTE="MacInWin, post: 1827436, member: 396914"] One more thing: The way that the cell service does the most to speed up the GPS fix is that your cell phone can get the almanac data faster over cell using a bit of your data allowance so that as soon as it has ephemeris data from 4 satellites, you have a fix. Normally that's in less than a minute, which can be disguised in the start up routine for the GPS application on the phone. To you, it looks practically instantaneous, but a lot of stuff is going on in the background to make it happen. EDIT: One more one more thing. GPS (or SatNav) will be showing where you WERE, usually about a second ago, as it takes some time for the signals to arrive, the fix to be calculated and the map updated. The navigation software anticipates that delay and forecasts where you SHOULD BE based on speed and direction you travelled a second ago. Normally, that forecast is correct, but sometimes it's not. If you are directed to take a turn and do not do so, it takes a second before the GPS fix shows you not there, and two fixes to figure out what direction/speed you did travel. So the map software assumes you took the turn, projects where you SHOULD BE if you did turn and has to correct when it figures out you didn't turn. That delay is why you see the map jump a bit at turns you ignore. [/QUOTE]
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Apple Mobile Products: iPhone, iPad, iPod
iPhone Hardware and Accessories
The downside of buying a used iPhone
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