poor mans electronic compass?

[bill fish]

Hi all

Had an idea regarding "electronic" compasses....compi?

if i understand it correctly....they use solid state electronics to detect the earths magnetic field and orientation.....pretty handy...possibly allows for electronic data taking/storage/downloading...and non moving parts means that can at least in theory be made fairly rugged...

I also seem to recall two downsides....pretty expensive and only really expensive ones have the accuracy desired for cave surveying...

Now,,,,,with a good old hand held sunto for example...the accuracy is sufficient......but in my experience the biggest pain with the hand held opticals is READING the darn thing...making sure that tick mark is actually say 197 and NOT 193 for example...and a close second is having to record the info...

Has anyone tried something like this?

Take you typical handheld/optical/mechanical compass....put an electromagnet on it.....then you turn on the field.....magnetic compass CARD?/ orients to electromagnet.....THEN when magnetic field is turned back off the card reorients with magnetic north...

So, if you have an optical widget that could then count the "tick" marks as the card reorients to magnetic north....you'd have an electronic measurement of true north that should be as accurate as hand held compass...

You'd probably have to make your own custom compass card....but maybe you could get pretty fancy with the optical reading part and get by with commercially available cards...

Any comments?

Blll

[Bob Thrun]

if i understand it correctly....they use solid state electronics to detect the earths magnetic field and orientation.....pretty handy...possibly allows for electronic data taking/storage/downloading...and non moving parts means that can at least in theory be made fairly rugged...

I also seem to recall two downsides....pretty expensive and only really expensive ones have the accuracy desired for cave surveying...
[/quote']
The problem is tilt sensitivity. The digital compasses measure the magnet field in the plane of this sensor. The Brunton Nomad is about $70, which is not expensive.

I talked with one of the Brunton engineers a couple of years ago. I suggested putting the magnetic sensor into one of the pocket transits that have a circular level. He said that that it would be as accurate as the pocket transit, but did not go into details.

Take you typical handheld/optical/mechanical compass....put an electromagnet on it.....then you turn on the field.....magnetic compass CARD?/ orients to electromagnet.....THEN when magnetic field is turned back off the card reorients with magnetic north...

So, if you have an optical widget that could then count the "tick" marks as the card reorients to magnetic north....you'd have an electronic measurement of true north that should be as accurate as hand held compass...

Blll

You have nearly described the first Brunton digital compass that was shown at the NSS Convention in 1975. It did not requite any electromagnet. It had the permanent magnets attached to a rotating card. There were sensors to measure the position of the card.