Re: [mowbot] Questions?

david steinke (dsteink nospam at
Mon, 03 May 1999 08:50:18 -0700

Dave Everett wrote:
> >a. How sensitive are the electronic compasses to permanent magnet motors
> >nearby (within 4")?
> >
> The short answer is, quite sensitive. The problem is that a motor is
> hundreds of times stronger than the Earth's magnetic field. Don't let that
> discourage you though, a bit of experimentation should find you a spot
> where the motor field is too weak to effect the compass. Field strength is
> the inverse of the sqr of the distance.
> Take into account heading errors caused by tilt. If your lawn is not flat
> you may experience substantial error. From the Vector manual "For example,
> in Mountain View, CA, for each 1deg of tilt, there would be about 3deg of
> heading error. In Greenland, for 1deg of tilt, there can be 10deg of
> heading error. I bought the 2XG model for this reason, it has gimballed
> sensor coils which can tilt up to 15deg to remain level.
> Dave Everett

Sounds like too many sources of error. I was hoping for the $5 solution.
I guess I will investigate a alignment beacon.