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 22:29:45 GMT
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Original-From:
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Chris Elliott <chelliot@cisco.com#AvoidSpam#>
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Viewed:
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648 times
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Vihung,
Now that selective availability is off I routinely get 12-18 feet accuracy
from my GPS. And, yes, the more satellites you've acquired and the more
spread between those satellites the better your accuracy. Also notice that
your relative accuracy will be much better than that--so if you can relate
your robot's actual position to a set of GPS coords then you'll be able to
use that relationship to determine subsequent positions more accurately.
Not sure how much drift you'll get.
Another issue is that GPS works better outside than inside. You'll get at
best poor reception in a house depending upon the ceiling/roofing
materials.
Most navigation systems for cars integrate knowledge of the roads and
will "snap" your location to a road. Some of them also integrate
speed/inertia sensors to react quicker and more accurately to changes in
speed and direction.
What would be useful for a small indoor robot is a local positioning
system. parkwatch.com has a system they are marketing to amusement
parks. There are many others. Don't know if there are any cheap/easy ways
of doing this.
Chris.
On Thu, 4 Jan 2001, Vihung Marathe wrote:
> 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.
>
> 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?
>
> 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
>
> -- V
>
>
Chris Elliott CCIE# 2013 | |
Customer Diagnostic Engineer ||| |||
RTP, NC, USA ||||| |||||
919-392-2146 .:|||||||||:|||||||||:.
chelliot@cisco.com c i s c o S y s t e m s
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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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