Re: [mowbot] What Happene

Raymond Skarratt u (skar9500 nospam at
Sat, 23 Nov 1996 16:39:26 -0500 (EST)

On Fri, 22 Nov 1996, ALANXBALLWEG wrote:

> As I understand it, you can either set up your own differential beacon
> (expensive) or use one from one of several new services springing up who
> broadcast the differential signals over large areas. Does anyone have
> more ideas/information about this method of obtaining position fixes?
> Any other ideas of how to obtain ~20cm positional accuracy?

We can probably get <10cm accuracy with ultrasonic beacons, depending on
humidity and temperature variances. I think that the idea of having
three beacons and having the beacons listen to different frequencies (or
having the beacons give off different frequencies). Mowbot then sends
out a signal for the beacons (or beacon if the beacons are listening for
different frequencies) to 'ping' and then waits for the signal to come
back. Take the flight time of the sound and divide by 2 (sound goes out,
then comes back) and you have the distance (via speed of sound
calculations) to that beacon. Do that 2 more times and you know your
exact position as long as you know where the beacons are.

What would be nice is the ability to travel a straight line (like a
property boundary) using this method somehow. I know that it must be
possible but I can't really think of how to do it at the moment. Any
ideas? I'm trying to think of a way that would involve the least amount
of calculations.

We should probably start moving a little more quickly on this project. I
have been really busy the last month or so (mid to end of semester stuff)
so I haven't really had that much time to do anything but school.
However, as Xmas approaches and the semester ends I will have more and
more time but then as we approach march/April I will start to run out of
time again. I hope that we can have some definate plans and maybe even a
working prototype (sp?) out there somewhere by the end of April to Mid
may or so. I hope that's not too ambitious.

Anyway, Lets keep the conversation up and see what we can come up with.