Re: Maps! (let's have a seperate thread, instead of using roll call)




"Eddie Langdown" <the3lang@xxxxxxxxxxxxxx> wrote in message
news:D8ydnXotTrNC-hfZnZ2dnUVZ8t2dnZ2d@xxxxxxxxx


However, in upland mountain areas and in bad visibility an error of 185
yards per mile could be a problem.

Absolutely!

GAGS


Well!
I stand corrected Stevie, Steve & Gags !

Corrected? I wasn't correcting you, I was merely taking an opportunity to
see that you were better informed. I wouldn't dream of correcting a wise ol'
sage such as you! :-)

Thankyou!

You're welcome.

I am totally pants at maths,
but to be 185 yards out after a mile's walking with a 2 deg error!

Er...now I have to correct you! It was an additional 6 deg W error, i.e.
your 8 deg W compared to the correct figure that is probably nearer 2 deg W.

That is a huge distance... I had no idea.

Er... not really.

Think about what it means practically on the ground. For example, you pull
out your map and take a grid bearing from your HQ on say a church with a
steeple one mile away, you now add 8 deg W for magnetic variation, and sight
along the compass to your objective. You'll find, if your reasonably
accurate, that your direction of travel arrow points just to the right of
the church (if you can see it), probably no more than a few tenths of an
inch to the right from your 1-mile distant view. Do you say: 'Cor blimey
Guvnor some bugger's moved the church!' or 'The Church is in the wrong
place'. Er, no. You will suspect that there is a small error maybe due to
your setting or the compass or the way you're holding/pointing the compass.
Doesn't matter anyway! You're so close to what you can clearly see is your
objective. Do you now, head down, focus on the the compass at all times,
walk on mile and declare when you get there: 'The ruddy church has gone!' or
do you just walk to the church on the most easily accesible line/route? You
do the latter of course!

There again you'll probably tell me that the church you're looking for is in
the middle of dozens of others all spaced a few hundred yards apart! Even if
you can't see it, you'll target an intermediate feature, walk to that, and
then leapfrog on. You're still not going to be more than a couple of hundred
yards out and for a big feature that shouldn't be a major problem.

Of course it's very different if you're in a featureless environment or
visibility is poor. Then 185 yards can be very significant. And if there's
danger about then you need to think a bit more and use your compass in
conjunction with some additional/advanced route choice/directional
techniques.

I had imagined it would be a few feet and that these accurate devaitions
were just for airline pilots and ship's captains.

Airline pilot, ship's captain or scout leader, it's all the same. Why 1 or 2
deg are very important for the former two roles is that their journeys
happen over much longer distances than a mile. For a journey of 100 km an
error of 6 deg W equates to being over 10 km out of position!


So, I need to teach 2 deg now?

You need to teach that when converting from grid to magnetic bearings you
need to add the magnetic variation given on the map and vice versa. For OS
maps the magnetic variation and its rate of change are given in the key.
That's what you use. You should also use an up to date map as far as is
reasonably practicable; that should be one from the OS Explorer 1:25 000
series or equivalent. (Anything older than 2000 I would consider replacing
if possible.)


As to using compasses in what you call 'lowland areas', I would say it is
just as important as anywhere.
What we have around London, and what is our 'bread and butter' hiking, are
millions of tiny footpaths, some only a few hundred yards long, and
differenciating one from another is continual detective work.... I love
it.

Good! If you keep map and ground in 'contact', your map oriented, and you
'thumb' the map, you shouldn't have major problems

The typical problem is when you come through a field to a small lane,
which
looks exactly like a dozen roads in the area, but which road?

If you have to ask which road, then the question that preceeded it must have
been: 'Which field am I in?'! You should know which road it is. The question
then is: 'Which way do I turn when I reach the road?'. I'll say again: If
you keep map and ground in 'contact', your map oriented, and you 'thumb' the
map, then this question should be relatively easy to answer!

And a compass
is usually the key to discovering the right road.

Eh? A compass doesn't tell you which road! A compass doesn't have a brain or
a memory! It's a dumb piece of kit. Jeez Louise, leave it on the ground and
the needle points N. Ask it a question and the needle points N. Do a jig
around it and hurl a thousand insults at it and the needle still points N!

A compass is secondary to the map. The map will tell you which road. The
compass, used with the map, may help to tell you which road.

I have walked in most of
the wild places in the UK and have often walked on a circular route of
only
three or four long footpaths/ bearings. A typical hike around Surrey/
Kent
could easily involve 50 path junctions and each needs to be checked with
map
and compass.

Not always. Have your map set, keep your map set, read it, use things such
as attack points, and most route change decisions come down to left, right
or straight on. There are hundreds of clues to help you right there in front
of you on the map.

What you look for when setting a route that keeps scouts off of
roads is a 'run' of dozens of short paths that get the walker from A - B.
Of
course, the chance of a compounded error is huge especially as paths go
through gardens and farms where signs have been removed etc etc.
I really can't say that walking here is any harder than walking in
mountains
but it is all we have locally and is a totally different skill .

No, you largely use the same set of skills but some to different degrees.

And strangely, you often meet no-one for hours on end.

Probably because everyone else is at home watching the football! :-)

Where-as when I was in the Black Mountains last week, it was like
Piccadilly
Circus!

A little over-exaggeration, but I know what you mean!

And there was I on Dartmoor last week and in many parts it was empty!

GAGS


.



Relevant Pages

  • Here you go Larry, a good map and compass primer
    ... Using map and compass together ... orient a map as well as how to correct for variation. ... Next, orient the map. ...
    (misc.survivalism)
  • Re: GPS Vs COMPASS
    ... If I am still walking in 10 years time I will still be ... >>>using my compass to orient my map and to take bearings when it is not ... A GPS ...
    (uk.rec.walking)
  • Re: GPS Vs COMPASS
    ... >>using my compass to orient my map and to take bearings when it is not ... A GPS ... And if you happen to have chosen a route that does not lead almost ...
    (uk.rec.walking)
  • Re: GPS Vs COMPASS
    ... > using my compass to orient my map and to take bearings when it is not ... > Clearly you must be using your GPS merely as an emergency device ... > checking your route is correct by consulting your map in combination ...
    (uk.rec.walking)
  • Re: 1507 text ref of Inventio Fortunata
    ... >> You mean I'm not cowed into believeing your clouds of squink? ... Rusch only had to hear the reports of the squiffy compass behaviour. ... There was no need for the Norse to map Greenland for him while they ...
    (sci.archaeology)