Why does my N900 look for internet connection to use GPS?
 

I called Nokia support and was told that N900 is not a real GPS device hence it requires an internet connection.

Re: Why does my N900 look for internet connection to use GPS?
 

That's not true for sure. It just takes ages to get an sat-fix w/o a-GPS.

Re: Why does my N900 look for internet connection to use GPS?
 

i think we have assisted gps, it uses the internet to get a rough location, cutting down the time it takes to get a satellite connection since it knows where to look (i generally think 'up' is the correct direction to look for sattelites, but what do i know.)

Re: Why does my N900 look for internet connection to use GPS?
 

The nokia support is wrong in that statement. The n900 contains a real gps antenna.. however its weaker compared to car navigation devices gps antenna..

Therefor it uses what is called a-gps (assisted gps) and accesses internet to get information on where current gps salitelites are located in the sky, wich will help get a quicker gps fix.

Its possible to get a gps fix without internet, but it might take longer, and things like weather and buildings and such might have a big impact on how fast you get a fix.

Re: Why does my N900 look for internet connection to use GPS?
 

This is the key. If you use the assisted gps using internet, it will help to get the current position within seconds rather than "minutes".

Re: Why does my N900 look for internet connection to use GPS?
 

Why is it so hard to calculate where the satellites are with reasonable accuracy? If you know their position in a point in time it's just a mater of doing some math to get their position at any moment in the future (the far the two moments are the worse the accuracy is, but i wouldn't expect it to get too bad in just a couple of days, and whenever there is a connection to the internet it can re-zero the positions to a more accurate measurement.

Re: Why does my N900 look for internet connection to use GPS?
 

Are the satellites geostationary? If that's the case, you can't do any math to find them. Then you need to get some other fix, like using 2G/3G antennas.

Re: Why does my N900 look for internet connection to use GPS?
 

No, they spin around the earth in a spherical constellation all at pretty mucht he same altitude; it's fun to watch speed up animations of them going around trying to figure out the path of a single one, it's kinda an optical illusion, kinda looks like they will collide or make an extreme turn when reaching the poles.

Re: Why does my N900 look for internet connection to use GPS?
 

I think the problem with this calculation is that the clock of the N900 would not be accurate enough. You can calculate the position of the sattelite, but you never know if your "now" is exactly the same as the sattelites "now".

Re: Why does my N900 look for internet connection to use GPS?
 

I wouldn't expect the error in the position would be big enough to make the result of the calculation useless.

btw, here is an animation of the satelites orbiting:

http://upload.wikimedia.org/wikipedi...llationGPS.gif
(in this one the effect i mentioned in my previous post isn't noticeable_

according to the source it says time is sped up 2880 times making one day go by in 30 seconds, and the time of a single orbit of a single satelite is 12 hours, i think those numbers would probably be enough to calculate how many degrees per minute the satellites move in the sky.

Re: Why does my N900 look for internet connection to use GPS?
 

@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.

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.

Re: Why does my N900 look for internet connection to use GPS?
 

So it's really a software matter?

Re: Why does my N900 look for internet connection to use GPS?
 

Thats what i meant.

Re: Why does my N900 look for internet connection to use GPS?
 

To get some closure on this topic: Starting up gpsjinni before opening Maps helps get a lock even without an Internet connection. I guess the Maps developers should beg/borrow/steal the code from gpszinni.

Re: Why does my N900 look for internet connection to use GPS?
 

n900 uses internet connection to even download maps as per the coordinates it receives from the gps chip...


in case it wasnt already stated in the thread :)

Re: Why does my N900 look for internet connection to use GPS?
 

Ovi Maps does not download new maps, if they were pre-loaded.

Other map applications may download map data (or some allow it to be preloaded).

Re: Why does my N900 look for internet connection to use GPS?
 

how much space reasonable vector maps of all the most common places where people are expected to bring their N900 to would take?

Re: Why does my N900 look for internet connection to use GPS?
 

To strip this down and answer some hardware and gps-tech questions.

If it asks for network connection depends on your settings -> location.

The word you are looking for is "Satellite Cache" which will be downloaded (or better just recieved) from satellites at view.
This may take up to 12 minutes and at least 120 seconds.
The antennas power is pretty good as I get a fix in some buildings from reflection and/or direct signal. In case of A-GPS the onboard system downloads the cache from a server which has information from a nearby stationary GPS system. How does it know where you are? It knows the celltower-IDs around you.

Easy! No you can't! Why? If that would be possible you would get a fix in the second you get the ID of 3 sats.
The US military updates satellite's positions, some go offline for maintenance and come back up at another spot as one died and so on. Normaly you get a fix if you had one in the last 24h at the spot where you turned your gps off but not for sure. They are drifting and correction of positions are calculated constantly.

Please at least try to read on some information before you ask general questions on hardware and technical functions of things like "how does gps work?" Most of the hardware specs are at wiki.maemo.org... (just read the 100s+ thread asking about the IR device)

Re: Why does my N900 look for internet connection to use GPS?
 

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.

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.

Re: Why does my N900 look for internet connection to use GPS?
 

I remember a while ago i was in a cell phone store, from a carrier, another customer was browsing and asked if a certain model had GPS, i knew it had, i told him, but the chick from the store insisted he would have to hire the GPS service from the carrier, as if it wasn't a physical property of the device itself, it was a lost battle :(

Re: Why does my N900 look for internet connection to use GPS?
 

Re: Why does my N900 look for internet connection to use GPS?
 

@j.s - thanks for the clarification re: atomic clocks and timing; i should have just read wikipedia before posting.

re: nokia being 'lazy' with software... gpsjinni gets a lock in sensible time without data but "Ovi Maps" can't. you can switch to ovi maps when you get a lock on gpsjinni and it works. this must be a software issue?

my N95 didnt have A-GPS and could get a GPS lock without data. this hardware and design predated the N900 by 2 years. means/proves nothing in particular for the N900 but worth mentioning?

Re: Why does my N900 look for internet connection to use GPS?
 

How long is a piece of string? FWIW you can download all the available Ovi Maps for offline use onto an 8GB card (uses about 7GB of space).

Re: Why does my N900 look for internet connection to use GPS?
 

Actually you can, sort of, and it is exactly what modern-day dedicated GPS units attempt to do. Using their internal clock, the last received almanac and ephemeris data and operating under the assumption that they are still near the position the unit was last used (which, for most practical everyday purposes, usually holds true), they extrapolate which satellites are/should be visible to speed up the Time To First Fix considerably. These mechanisms, known under a variety of trade names, are common in today's dedicated consumer GPS equipment -- hence creating the illusion for the masses that GPS is a turnkey system, when essentially it is far from it.

Personally, I think it should be possible to implement this "offline AGPS" behaviour on the N900 easily enough, improving the general perception of its GPS hardware quality (which indeed is quite good). Anybody know if there is any documentation available on how to feed the AGPS-data to the GPS receiver?

Regards,
Chris.

Re: Why does my N900 look for internet connection to use GPS?
 

have you tried your n95 again since the n900?i keep mine in the car as a backup satnav incase i need to save charge in my n900, the sat lock is achingly slow now, especially in town centres near high buildings, and even with the sim removed and offline profile selected it will still nag for an internet connection every 2 minutes.

Re: Why does my N900 look for internet connection to use GPS?
 

So not content with releasing half-finished products Nokia also builds in obsolesence to degrade their devices over time? ;)

Re: Why does my N900 look for internet connection to use GPS?
 

You can get a lock with agps inside a building where GPS satellites are not visible. It will be far from perfect, but you can at least get aproximate location.