Re: General GPS Question
On 30/10/2008 19:44, Matthias Camenzind wrote: I thought right now near same like you. I thought about the speed of satellites, But also right now i had another idea. With the signal form two satellites, and a known high over sea it should be possible to locate you on north or south of earth (only two possibilities). This would be nice if you go on a mountain and you are standing in front of a signpost (google translated) with meters over Sea value to get faster your first fix. You won't get a faster first fix because you concentrate on two satellites. The ublox receiver is able to track up to (AFAIR) 16 satellites at the same time. The *main* way to speedup the TTFF is to have almanac and optionally ephemeris available on the FR. Almanacs are valid for one week so it's easy to make sure you have up to date almanac before you go on a mountain :-) A simple question Are you in the North of earth? would be enough to get only one possibility. Unless you did a long plane travel before switching on your FR, the last known position would be enough. Many satellites will be visible in Madrid and in Paris at the same time for example. Abdel. ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: General GPS Question
On 30 Oct 2008, at 19:05, Matthias Camenzind wrote: Or if you have an altimeter with you. Something like this: http://www.princetonwatches.com/images/watches/53957.jpg Seems to be small enough to get in Gta03 or 04. :) The blades would prevent international air-travel with any equipped cell-phone. ;) Seriously, altimeter chips have been mentioned on this list in the past, when proposals have been made for including an altimeter. But an altimeter is unlikely to reach a production Openmoko phone because the demand is too small. Stroller. ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: General GPS Question
2008/10/31 Stroller [EMAIL PROTECTED] Seriously, altimeter chips have been mentioned on this list in the past, when proposals have been made for including an altimeter. But an altimeter is unlikely to reach a production Openmoko phone because the demand is too small. I wasn't proposing that the altimeter would have to be *in* the phone. You might have one in your wristwatch, for instance, or in your pocket... ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: General GPS Question
Matthias Camenzind wrote: Shouldn't it be possible to get the own position from three signals from the same satellite? The result would not be as exactly as from three or more but even better then no result. Why should it not work? No, because GPS run calculation triangulation from the signal coming from 3 different points. It the signals arrive from the same point, it will be impossible to obtain your position, because the signal itself doesn't contains any position info. ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: General GPS Question
You can only get current time from one satellite. It is not possible to compute your current position. It would be possible, though, to find out what is the distance between GPS receiver and the satellite. This distance is the radius of one sphere. When you combine signals from three or fours satellites, you will get three/four spheres, and the intersection point is your current location. Kamil ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
RE: General GPS Question
You get time and ID, out of this two things you'll get position. . If you change first 'time' and thrid 'time' to second time it should be possible to get a position out of that. Date: Thu, 30 Oct 2008 19:03:16 +0100 From: [EMAIL PROTECTED] To: community@lists.openmoko.org Subject: Re: General GPS Question You can only get current time from one satellite. It is not possible to compute your current position. It would be possible, though, to find out what is the distance between GPS receiver and the satellite. This distance is the radius of one sphere. When you combine signals from three or fours satellites, you will get three/four spheres, and the intersection point is your current location. Kamil ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community _ Werden Sie Mitglied der neuen Windows Live Messenger Familie! http://get.live.com ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
RE: General GPS Question
The satellites are moving around. So on a different time the position is different. Date: Thu, 30 Oct 2008 19:00:29 +0100 From: [EMAIL PROTECTED] To: community@lists.openmoko.org Subject: Re: General GPS Question Matthias Camenzind wrote: Shouldn't it be possible to get the own position from three signals from the same satellite? The result would not be as exactly as from three or more but even better then no result. Why should it not work? No, because GPS run calculation triangulation from the signal coming from 3 different points. It the signals arrive from the same point, it will be impossible to obtain your position, because the signal itself doesn't contains any position info. ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community _ Die neue Generation der Windows Live Services - jetzt downloaden! http://get.live.com ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: General GPS Question
On Thu, 30 Oct 2008 18:09:47 + Matthias Camenzind [EMAIL PROTECTED] wrote: The satellites are moving around. So on a different time the position is different. There is a number called the dilution of precision which quantifies the factor by which the accuracy of the GPS reading is reduced by the positions of the satellites. For instance, if a reading were from three satellites all positioned close to the zenith, the accuracy would be reduced compared to how it would be if they were widely spaced apart. To see how this works, visualise how the GPS correlator calculates your position by the intersection of spheres centered on the satellites, and consider how this would be affected by an inexact measurement of the radii of the spheres. Then consider how that would in turn be affected by the positions of the satellites. While in theory your suggestion would work, the geometrical dilution of precision would be HUGE, and so the measurement would overall be very inaccurate. Tom -- Thomas White Department of Materials Science and Metallurgy Electron Microscopy Group (PhD Student) University of Cambridge / Downing College ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: General GPS Question
On 30/10/2008 19:09, Matthias Camenzind wrote: The satellites are moving around. So on a different time the position is different. First the satellites are not moving fast enough, and they are moving in the same direction of course, so you cannot really do triangulation (the three measurement will be in the same plane). Second your clock has an unknown bias that needs to be solved and that is changing at each second. So I guess you can forget about it :-) Abdel. ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
RE: General GPS Question
I thought right now near same like you. I thought about the speed of satellites, But also right now i had another idea. With the signal form two satellites, and a known high over sea it should be possible to locate you on north or south of earth (only two possibilities). This would be nice if you go on a mountain and you are standing in front of a signpost (google translated) with meters over Sea value to get faster your first fix. A simple question Are you in the North of earth? would be enough to get only one possibility. BTW: Agreed with Abdelrazak Younes (Mail entered while writing). Date: Thu, 30 Oct 2008 18:24:26 + From: [EMAIL PROTECTED] To: community@lists.openmoko.org Subject: Re: General GPS Question On Thu, 30 Oct 2008 18:09:47 + Matthias Camenzind wrote: The satellites are moving around. So on a different time the position is different. There is a number called the dilution of precision which quantifies the factor by which the accuracy of the GPS reading is reduced by the positions of the satellites. For instance, if a reading were from three satellites all positioned close to the zenith, the accuracy would be reduced compared to how it would be if they were widely spaced apart. To see how this works, visualise how the GPS correlator calculates your position by the intersection of spheres centered on the satellites, and consider how this would be affected by an inexact measurement of the radii of the spheres. Then consider how that would in turn be affected by the positions of the satellites. While in theory your suggestion would work, the geometrical dilution of precision would be HUGE, and so the measurement would overall be very inaccurate. Tom -- Thomas White Department of Materials Science and Metallurgy Electron Microscopy Group (PhD Student) University of Cambridge / Downing College ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community _ Die neue Generation der Windows Live Services - jetzt downloaden! http://get.live.com ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: General GPS Question
2008/10/30 Matthias Camenzind [EMAIL PROTECTED] This would be nice if you go on a mountain and you are standing in front of a signpost (google translated) with meters over Sea value Or if you have an altimeter with you. ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
RE: General GPS Question
Date: Thu, 30 Oct 2008 18:51:14 + From: [EMAIL PROTECTED] To: community@lists.openmoko.org Subject: Re: General GPS Question 2008/10/30 Matthias Camenzind This would be nice if you go on a mountain and you are standing in front of a signpost (google translated) with meters over Sea value Or if you have an altimeter with you. Something like this: http://www.princetonwatches.com/images/watches/53957.jpg Seems to be small enough to get in Gta03 or 04. :) _ Werden Sie Mitglied der neuen Windows Live Messenger Familie! http://get.live.com ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
