Subject:
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Re: GPS
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 4 Jan 2001 22:27:49 GMT
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Viewed:
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536 times
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In lugnet.robotics, Vihung Marathe <vihung@marathe.net> writes:
> OK. This is probably a bit off-topic ... but I am sure you will find
> this interesting ...
>
> I recently rented a car from Hertz with the NeverLost system - GPS
> Receiver, Street Maps and Business/Tourist directory built into one.
> Apart from the fact that I found this EXTREMELY useful (so useful in
> fact that I am looking for a similar system to install in my car), I
> also found it very accurate. Far more accurate than the 30 meter
> resolution that civilian GPS is supposed to offer.
Since some month the accuracy is about 12 -15 meters.
(When I'm right, then there was an error added before to lower accuracy)
>
> I was pondering over how this can be for most of my trip ... until I
> drove somewhere where it could not find any satellites (blocked off by
> buildings and such). As I moved, more and more satellites came into view
> ... but it would not show my position on the map until it could see 6
> (it had an indicator showing how many were in view in place of the map).
>
> Now I am not sure about this ... but if I remember my high school
> geometry correctly (and I think I remember reading this in an article
> about GPS some time ago when it first became popular) ... you only need
> three satellites in view to pinpoint your location. If that is the case,
> then do you get better resolution with more satellites?
You get a better resolution if the signal of the aother satellites is better
(a higher level) The measurement-techniques are very difficult. (They find a
little signal in a lot of noise). Only three satellites will work (i guess),
but the more, the better. (The navigation tool choses some satelites)
> The reason I ask this here is that some time ago, I was wondering if GPS
> could be used to pinpoint the position of a Lego robot - but then
> realised that it would be of no use within a room, because the room
> would be smaller than 30m that GPS can resolve. However, if it is
> possible to get more info using more satellites, then maybe we can think
> about it
We had an approach using GPS with robotics (not with Mindstorms indeed).
We noticed that the only way to use GPS is to have a differential GPS. There
you have a reference station, which knows its exact position. This station
looks at the satelites and computes the error from the satelites and sends
it on a radio frequency. We reached 1-2 m accuracy.
http://www.informatik.fh-hamburg.de/~lego/Projekte/f18/f18.html
(only in german)
The MARVIN project at TU-berlin reaches 2cm
(Multi-purpose Aerial Robot Vehicle with Intelligent Navigation )
http://pdv.cs.tu-berlin.de/MARVIN/index.html
Rainer
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Message has 1 Reply:
 | | Re: GPS
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| (...) As a footnote: Notably, when SA is turned on, both GPS units must use the same satellites for this to work. (24 years ago, 4-Jan-01, to lugnet.robotics)
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Message is in Reply To:
| | GPS
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| OK. This is probably a bit off-topic ... but I am sure you will find this interesting ... I recently rented a car from Hertz with the NeverLost system - GPS Receiver, Street Maps and Business/Tourist directory built into one. Apart from the fact (...) (24 years ago, 4-Jan-01, to lugnet.robotics)
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