Thread: Why does my N900 look for internet connection to use GPS?
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j.s is offline j.s
2010-08-31 , 22:27
Posts: 486 | Thanked: 251 times | Joined on Oct 2009
#19
Originally Posted by cashclientel View Post
@gunni - no GPS unit uses it's internal clock. The time differences involved require an atomic clock. This baby sits in space as part of the system and is one of the sattelites you need a lock on for GPS to work.
Any four GPS satellites are enough to get a fix (unless they all lay along a straight line from the GPS receiver point of view). Three are enough if the receiver elevation is known.

There is no special GPS satellite for time. The reason one more degree of freedom is required than for the purely geometric calculations is to figure out what the time is at the GPS receiver.

All each satellite transmits is its ID, the time, and what its ephemeris is, over and over, very slowly. The receiver needs to calculate its time, where each visible satellite is, and measure the distance to each satellite. Then it calculates where it is. It measures the distance to each satellite by subtracting the time the message was sent from the time that it arrived.

Originally Posted by cashclientel View Post
N900 requires a net connection to get a lock because Nokia were too lazy to work on the device and code to make it function otherwise.
That is an unfair oversimplification.

However, the refusal to give up nagging for an internet connection after the user has repeatedly rejected is another matter.
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