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Subject: 
Re: How many people signed up for the NXT Developer's Program?
Newsgroups: 
lugnet.robotics
Date: 
Wed, 18 Jan 2006 19:56:00 GMT
Viewed: 
1679 times
  
In lugnet.robotics, Mr S <szinn_the1@yahoo.com> wrote:
--- John Brost <john.brost@gmail.com> wrote:
The first thing I thougth of when I heard of the
NXT's bluetooth capability was
getting it to recieve GPS data from my bluetooth GPS
receiver.  Obvious NeXT
step... a GPS guided LEGO rover.

John,
Seeing that GPS accuracy is on the order of several
yards (optimistically speaking) what LEGO robot wouuld
you build that could make good use of GPS, and how
would it use GPS?

Cheers

S

I have a great deal of experience with GPS. The accuracy you mention is indeed
correct (the GPS I'm looking at right now is specd at 5 meters horizontal
accuracy).  However, when you look at second-by-second accuracy, it is much
better.  A great deal of the error in many GPS receivers is caused by drift,
which is how much the reported position of a stationary object moves over time,
usually over the course of several hours.  When mobile, the drift isn't so much
of a problem, unless you are trying to drive in the same circle for hours on
end.  The GPS unit I'm specifically thinking about using is one of the better
ones for this sort of thing, and given a clear view of the sky, I think it would
do okay.  I've been impressed with its performance so far in other applications.
I could even do a running average on the reported coordinates to clean up any
errors.  Your concerns are indeed valid, but my experience and intuition tell me
it can be done.

Obviously I'm not going to have something that is highly accurate, but I am
pretty confident that I could get something to follow a course within 3 feet or
so.

As for a good use for such a robot, well I never said I had a good use for it,
besides the fact that I think it would be cool to do! :)  After all, why do
people climb Mt. Everest?  Because it is there.

Maybe navigating autonomously to pre-programmed points, sort of like outdoor
line following without the line.  If I got really ambitious, I did find this
event called Robo-Magellen, which appears to be an autonomous outdoor robot
competition similar to a mini-DARPA Grand Challenge.

http://www.robothon.org/robothon/challenge.php

Could be interesting, but it would need more than just a GPS for guidance, maybe
the NXT's ultrasonic detector for obstacle avoidance.

John



Message has 2 Replies:
  Re: How many people signed up for the NXT Developer's Program?
 
John, The reason I asked is that to get a Lego robot that is moving enough to even use GPS (read moving more than 5 yards, and outside no less) it will take a special build. Your *average* differential drive/steer robot with castor is not likely to (...) (18 years ago, 18-Jan-06, to lugnet.robotics)
  Re: How many people signed up for the NXT Developer's Program?
 
(...) I totally agree. Try playing with GPS 'cos now you'll be able to! The RCX was so limited by only being able to read a single dimensional value with an effective accuracy of about 1%. I've played with GPS a fair amount too and your description (...) (18 years ago, 18-Jan-06, to lugnet.robotics)

Message is in Reply To:
  Re: How many people signed up for the NXT Developer's Program?
 
(...) John, Seeing that GPS accuracy is on the order of several yards (optimistically speaking) what LEGO robot wouuld you build that could make good use of GPS, and how would it use GPS? Cheers S (18 years ago, 18-Jan-06, to lugnet.robotics)

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