Subject:
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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 22:06:41 GMT
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Original-From:
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Vihung Marathe <vihung@marathe.&nospam&net>
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Viewed:
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576 times
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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 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
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Message has 4 Replies:
 | | Re: GPS
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| (...) The reason you are getting better resolution is the US Government turned off selective availability (the random noise inserted into the timebase, then encrypted so military applications can use it). They reserve the right to turn it back on in (...) (24 years ago, 4-Jan-01, to lugnet.robotics)
| | | RE: GPS
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| GPS requires a clear, unobstructed view of the satellites in the sky. Forget about using it indoors. Earthquake researches use sensors that can detect movements of less than an inch. I don't know how they work, but it involves GPS to some extent. (...) (24 years ago, 4-Jan-01, to lugnet.robotics)
| | | Re: GPS
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| (...) Since some month the accuracy is about 12 -15 meters. (When I'm right, then there was an error added before to lower accuracy) (...) You get a better resolution if the signal of the aother satellites is better (a higher level) The (...) (24 years ago, 4-Jan-01, to lugnet.robotics)
| | | Re: GPS
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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 (...) (24 years ago, 4-Jan-01, to lugnet.robotics)
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