Subject:
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Re: GPS Reality?
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Newsgroups:
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lugnet.robotics
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Date:
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Sat, 9 Apr 2005 17:55:35 GMT
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Original-From:
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Steve Baker <SJBAKER1@stopspamAIRMAIL.NET>
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Viewed:
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1194 times
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Andrew G. Meyer wrote:
> Is the idea of a GPS sensor compatible to the sensor ports an absurd idea? I
> have a few old Garmin units, with RS232 ports on them. I know of people who have
> incorporated these units successfully into "real" robots, but that usually
> involves heavy PCB construction and a BASIC Stamp. Shame HiTechnic isn't selling
> anymore... their compass looked appealing.
It's probably possible - making an infra-red transmitter to sit on the GPS side
would get you there if the GPS could be made to run at a low enough baud rate.
Alternatively, you could modify the RCX to take in RS-232 directly...but that's
almost certainly not the question you should be asking.
Standard GPS is accurate to AT BEST about 10 feet. Typically, 20 or even 40 feet
if there is no clear view of the sky, or if it's cloudy, under trees (especially
wet trees soon after rain). GPS reception is also MUCH worse when the GPS unit is
close to the ground - holding one up above your head generally gets you better
reception than holding at waist height for example.
Some older GPS units (from back in the days when the military insisted on encrypting
the low order bits of the GPS clock) are at best only accurate to 75 feet and at
worst to maybe twice that.
It's hard to imagine an application for a Lego Robot that would require it to travel
such large distances and to care so little for precision...but maybe you have something
very unusual in mind.
There is a system called 'differential GPS' which relies on an expensive specialised
'ground station' that you set up somewhere near where your robot will be operating.
That system improves resolution to an inch or less...I'm not sure whether an 'old
Germin unit' would support differential GPS...I suspect not.
Differential GPS will tell you where you are RELATIVE TO THE GROUND STATION with great
precision - but if the ground station has not previously been sited exactly by other
means, you won't know where you are on the surface of the earth to better than the
usual 10' type range.
---------------------------- Steve Baker -------------------------
HomeEmail: <sjbaker1@airmail.net> WorkEmail: <sjbaker@link.com>
HomePage : http://www.sjbaker.org
Projects : http://plib.sf.net http://tuxaqfh.sf.net
http://tuxkart.sf.net http://prettypoly.sf.net
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Message has 1 Reply:
 | | Re: GPS Reality?
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| Its worth pointing out that there has been recent discussions on the DPRG list about small scale location - a discussion which started off on GPS. I think it has now progressed to a system combining three sonar beacons, which are broadcast a radio (...) (20 years ago, 10-Apr-05, to lugnet.robotics)
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Message is in Reply To:
| | GPS Reality?
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| Is the idea of a GPS sensor compatible to the sensor ports an absurd idea? I have a few old Garmin units, with RS232 ports on them. I know of people who have incorporated these units successfully into "real" robots, but that usually involves heavy (...) (20 years ago, 7-Apr-05, to lugnet.robotics)
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