Re: Tesco Value Compasses

On 11 Feb, 18:14, alansplodge <a...@xxxxxxxxxxxxxx> wrote:
On Feb 11, 3:05 pm, GAGS <gags...@xxxxxxxxxxx> wrote:

They seem to be perfectly serviceable and point in the general
direction of magnetic north,

How much 'general direction'?

The one I looked at pointed the right way across the Tolmers flag-
circle; that is as near to empirical evidence as I have right now - I
didn't want to make any false claims.

IME 'cheap' compasses tend to have an accuracy of +/- 5 deg at best.
That's better than 'the general direction' but it's not something
you'd accept as adequate in feature-poor terrain.

But even a sewing-needle stuck
in a cork, in a saucer of water should accurately point to mag N
shouldn't it?

Yes it should align with the Earth's magnetic field. However, damping
(or rather the lack of it) is a major problem and neither will the
needle be balanced. Accurately? +/10 deg at best I'd say.

So claimed my Ladybird book "Magnets, Bulbs & Batteries"
when I was a Wolf Cub.

These compasses should do the job if you just want to set a map on a
10km footpath walk in the Home Counties.

Yes. For setting the map in a feature-rich terrain they should be more
than adequately up to the job.

I wasn't recommending them
for orienteering competitions

The compass is very much a secondary tool in orienteering. You very
rarely need to run on an accurate bearing. Only in a few events in
feature poor terrain (dense forest with few tracks, streams, fences -
i.e. few linear features) have I needed an accurate bearing to lead to
an attack point that is a point feature. Even in this terrain I'm
still using map features (reading contours, terrain shape, etc) more
than a compass.

or mountain expeditions.

Certainly here in unknown terrain a good quality protractor compass is
vital. Walking on a bearing is more common especially in trackless,
featureless moorland terrain and you'll likely be doing more
triangulation and resection to check route and position.

GAGS
.

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