Reply
Thread Tools
DeargDoom is offline DeargDoom
2010-06-06 , 23:31
Posts: 66 | Thanked: 70 times | Joined on Apr 2010 @ Paris
#1
From reading threads like this one I gather that most people have similar experiences to myself, ie with network posistioning a GPS position can be found within seconds but without one it takes several minutes if it works at all. In fact I have never succeeded in getting a GPS position without some data transfer.

Obviously this only becomes an issue for me when I am roaming and so dont want any open data connections but I am out of the country a couple of times a month so its a little annoying. What I have been doing up until now is opening a data connection until I have a lock on my GPS position and then closing the data connection. Once the initial position has been found I seem to be able to keep a reasonably precise track on my position indefinately, despite having no open data connections.

Apart from the hassle this is bothering me because I dont understand why this would be. What is the difference between finding your intial position and then keeping track of any changes to that position?

Any technical explanation of the N900 GPS positioning would be extremely welcome.
 
Edsal is offline Edsal
2010-06-06 , 23:40
Posts: 66 | Thanked: 11 times | Joined on Jan 2010
#2
ovi maps take's for every to load geeezz why can't we have google maps (the real one) not the maep can't do any seach on that.
 
stone17 is offline stone17
2010-06-06 , 23:44
Posts: 113 | Thanked: 52 times | Joined on Jan 2010
#3
I guess it doesnt matter if you do GPS positioning with the N900 or any other device. Its always the same. I am not an expert, but
1. The device needs at least 4 satellites to obtain a position, that is you have 3 spatial coordinates and time. you have 4 unknowns, so you need at least 4 satellites.
2. the gps frequenzy is different from the one your cellphone is using for calls, in this specific case, the carrier frequency for the gps signal is absorbed/reflected by most dense materials as stone, concrete or steel. Trying to get a fix within a concrete building is not possible.
3. While in a city with high buildings or while in a canyon, the signal may gets reflected, changing traveling time of the signal- You actually extract position from traveling time of the signal - makes it difficult to extract your position as well
4. why does it take long to get a fix and what is the difference from keeping the signal? a wild guess would be
You might run a chi^2 or a least mean square to do the actual triangulation, if you do this first, you have no starting point for your algorithm, later when you have the fix, you know where you have been, so you know what starting point to put in your algorithm.
It might be that way or something totally different...

I actually get a fix (pure GPS) within seconds, way faster than with my n95 8gb.
Last edited by stone17; 2010-06-06 at 23:48.
 

The Following 2 Users Say Thank You to stone17 For This Useful Post:
DeargDoom is offline DeargDoom
2010-06-06 , 23:47
Posts: 66 | Thanked: 70 times | Joined on Apr 2010 @ Paris
#4
Originally Posted by Edsal View Post
ovi maps take's for every to load geeezz why can't we have google maps (the real one) not the maep can't do any seach on that.
Actually I have the map data I need pre-cached so the ovi maps application itself is no big deal. All Im curious about is getting a GPS position, which can be done without ovi maps of course.
 
DeargDoom is offline DeargDoom
2010-06-06 , 23:59
Posts: 66 | Thanked: 70 times | Joined on Apr 2010 @ Paris
#5
Originally Posted by stone17 View Post
3. While in a city with high buildings or while in a canyon, the signal may gets reflected, changing traveling time of the signal- You actually extract position from traveling time of the signal - makes it difficult to extract your position as well
I was trying this in the outskirts of Dublin, which is low rise to no rise. Devices like TomTom seem to get a lock pretty quickly and I would have assumed that there is no data transfer there.

Obviously its unsurprising that a dedicated device outperforms my phone but Im curious as to what exactly is the difference between the two.

Also would inputting my approximate GPS position speed things up? I would have thought this would be possible with the phones cellular position.
 
stone17 is offline stone17
2010-06-07 , 00:04
Posts: 113 | Thanked: 52 times | Joined on Jan 2010
#6
Originally Posted by DeargDoom View Post
I was trying this in the outskirts of Dublin, which is low rise to no rise. Devices like TomTom seem to get a lock pretty quickly and I would have assumed that there is no data transfer there.

Obviously its unsurprising that a dedicated device outperforms my phone but Im curious as to what exactly is the difference between the two.

Also would inputting my approximate GPS position speed things up? I would have thought this would be possible with the phones cellular position.
I think, one reason for this might be a better receiver within the pure GPS devices. But still, my N900 works damn fast. I have issues with my N95 8GB (the receiver is hidden behind the slider), when i use it in new cars. They seem to have thicker chassis than old cars, absorbing more of the signal. I can only get a gps fix directly unter the windshield, not within the car.

I think A-GPS and cellular assisted GPS just work that way, but even than your position is only accurate within km or so.
 
razibhasan is offline razibhasan
2010-06-07 , 00:17
Posts: 7 | Thanked: 0 times | Joined on Mar 2010
#7
I have both N900 and Nexus One. Nexus One can't connect to GPS while I am indoor. With N900, it works better (although it takes around 10 - 15 seconds to connect).

Please note that I am using maep (google maps) since Ovi Maps doesn't have maps for my country.
 
DeargDoom is offline DeargDoom
2010-06-07 , 00:28
Posts: 66 | Thanked: 70 times | Joined on Apr 2010 @ Paris
#8
Originally Posted by stone17 View Post
I think A-GPS and cellular assisted GPS just work that way, but even than your position is only accurate within km or so.
I would have figured that cellular assisted GPS wouldnt need any data transfer since your phone knows what cell it is in just by virtue of being switched on. I would guess that if were that simple then the network assisted GPS wouldnt need an open data connection to funtion.

Am I missing something?
 
jaeezzy's Avatar
jaeezzy is offline jaeezzy
2010-06-07 , 00:28
Posts: 664 | Thanked: 160 times | Joined on Jul 2008 @ Australia
#9
Is N82's inbuild GPS receiver better than N900's? coz it used to get quick fix in N82 anywhere where its possible to get fix whereas N900 indoor is almost forever coz I have never got the fix indoor waiting before I lose patience whereas outside it has but taken quite long.(This is all without internet connection coz with the internet connection its ok)
Also, wasn't searching for places possible without internet in previous version of ovi map in N900? As I don't have any data plan and outdoor its kinda useless.

EDIT: AH!! got one indoor after 5mins..
Last edited by jaeezzy; 2010-06-07 at 00:32.
 
stone17 is offline stone17
2010-06-07 , 00:36
Posts: 113 | Thanked: 52 times | Joined on Jan 2010
#10
Originally Posted by jaeezzy View Post
Is N82's inbuild GPS receiver better than N900's? coz it used to get quick fix in N82 anywhere where its possible to get fix whereas N900 indoor is almost forever coz I have never got the fix indoor waiting before I lose patience whereas outside it has but taken quite long.(This is all without internet connection coz with the internet connection its ok)
Also, wasn't searching for places possible without internet in previous version of ovi map in N900? As I don't have any data plan and outdoor its kinda useless.

EDIT: AH!! got one indoor after 5mins..
The only place in the world where i (or anyone else) could possibly get a GPS fix indoors is within a wooden house. Back in Germany I never get a GPS fix indoors (European buildings are usually made of concrete), whereas in most US buildings (usually made of wood or cardboard) I can get a fix indoors, although it takes some time. This is not magic, absorption in wood is just less, just less enough so the the GPS receiver can pick it up.
 
Reply

« Previous Thread | Next Thread »

 
Forum Jump


All times are GMT. The time now is 02:44.

Contact Us - Home - Archive - Top