Silva Thumb Spectra

[Kitch]

anyone know of any good reason why E and W are reversed ?
or does it simply demonstrate that orienteers take no notice of the points of the compass ?

[keever]

When the needle points to "east" on the compass the compass is pointing east. Same for West

[keever]

anyone know of any good reason why E and W are reversed ?

No.

[Gross]

Andy.... you must remember asking Goran the same question... he came out with a reason that sounded sensible... but I can't remember what it was

[graeme]

1/ They aren't, its North and South which are reversed.
or
2/ They aren't - you're at the world Cup in NZ, so you have to hold the compass upside down.
or
3/ Your want your thumb to point along the bearing which the red arrow points to on the dial.

[Wayward-O]

I don't have one of these, but would suggest that it is because the N E W S are fixed, rather than on a rotating bezel. Therefore, instead of rotating the bezel to align N with the arrow and then reading off the bearing, it is the needle position that indicates the direction. I.e. if user / compass is pointing East, then the arrow will be pointing to E on the fixed markings.

[m4rk]

Yes. Because you're meant to memorise the colour and number of dots that the needle is pointing to when you're running on a bearing.

If E and W were the right way round, you'd be remembering 'E' when running west which would be most confusing.

[Kitch]

I worked it out whilst I was asleep, literally !!
middle of last night I had a very brief dream where I was watching the needle of a compass as I turned to face east.
The north end of the needle ended up pointing 90 degrees to the left of the N shown on the housing.
I then woke up - I think more in amazement that my subconscious mind had decided it need to answer the conundrum - I had'nt though about it atall that evening. I suspect that after 30 years of orienteering my mind felt that I really should know the answer.
Once awake I then spent quite a while thinking about the difference between a map and a compass.

A map shows you many things but the main point about a map is that it is a relative representation. For a map to work you need to know where you are and to have it oriented correctly. Once these two requirements are in place for any "where is?" question the answer is always "Over there". You don't need to know north, east, south or west for a map to work - as long as you keep it oriented and know where you are. You can orientate from known features on the ground. But we always put north on the map to allow us to use a compass to orientate it.

A compass needle is not relative. It does one thing and one thing only, it points north.
a compass is a tool built around the needle to help us make use of the single fact that the needle can tell us - "where north is"

So back to the why is E on the left of a spectra question.
in terms of a map, which is relative, you can ask any question you like
But because maps are invariably drawn "oriented" to north (north lines drawn on, north at the top, text oriented to match)
we invariably use the map based question asking ............................................"where east is relative to north?" the answer is east is 90 degrees right relative to north.

in terms of a compass needle,
where the only known is north, you have to ask where is north.....So; "where is north relative to east?" the answer is, north is 90 degrees left relative to east.

So if you want to head east the north needle needs to be pointing 90 degrees to your left.
the E on a Spectra is, says where the north needle needs to be pointing, you then follow the pointy bit of the compass to head east.

[graeme]

Yes, its designed so you can follow a bearing without using the map at all.

I don't ever try to run "east". I just run "90 degrees right of north". So although I've owned a series of these compasses, I never pay attention to the letters. I started using thumb compasses becuase i notice I never turned the housing on the compass.

At a recent WRE middle (Belgium - flat) I consciously switched to not using the map at all, just compass and pacing. One less thing to think about meant I speeded up and for control-picking style planning this seemed most effective. I've noticed this at the last couple of BOC middles as well, but because its not a skill I practice, I'm not very accurate (and forget to do it until midway through the course). Even at Inchmarnock, it was only when I ditched the detailed mapreading that I started moving at a decent pace.

How do others balance mapreading vs compasswork in middle races?

[Ali Wood]

Yes, its designed so you can follow a bearing without using the map at all.

At a recent WRE middle (Belgium - flat) I consciously switched to not using the map at all, just compass and pacing. ... I speeded up and for control-picking style planning this seemed most effective. I've noticed this at the last couple of BOC middles as well, but because its not a skill I practice, I'm not very accurate..... ......it was only when I ditched the detailed mapreading that I started moving at a decent pace.

How do others balance mapreading vs compasswork in middle races?

Well, that would be a sad state of affairs, if we could achieve respectable (winning) times on middle races using compass without map... either the area would have to be 100% runnable and devoid of features, or the planner would have to have got it wrong.

The idea of a middle is yes, to constantly switch directions, but it is also to force rapid decisions, like 'go straight or round?' or 'run up the spur or the re-entrant?', and maybe vary your speed using traffic lighting according to the features you tick off.

I suppose we should be grateful we don't have compasses which somehow guarantee we go in exactly the right direction!!

[Glucosamine]

I suppose we should be grateful we don't have compasses which somehow guarantee we go in exactly the right direction!!

After a fashion is that not the essence of GPS? Thankfully loading courses and maps is harder than for OS map based sports ... for now. A forest full of synthesised voices telling us to 'turn around when possible' in satnav style does not bear thinking of.

[Kitch]

will a GPS ever be able to calculate that, rather than taking the Bee line to the control it is is actually quicker, in this particular forest, to banana into the control, running up the spur and over along the ridge because there is less undergrowth and more rock and therefore, for this terrain, it is faster running. Never mind taking profile into account ....

[Gross]

will a GPS ever be able to calculate that, rather than taking the Bee line to the control it is is actually quicker, in this particular forest, to banana into the control,

But it might tell you to take first left, second right and watch out for the low bridge

[EddieH]

As one of the few times I've been in a car with GPS it kept saying turn left off the top of a 100m high bridge to get onto the road below, then turn round at the first available chance and try again.

I know that the delivery men that rely on it here can never find me. You'd think they's have learned that postcodes in the country cover vast areas, but apparently GPS is GOD.

[graeme]

will a GPS ever be able to calculate that, rather than taking the Bee line to the control it is is actually quicker, in this particular forest, to ....

In the particular forest I was referring to, yes...
http://omaps.worldofo.com/index.php?id=75100
(OK, you may not need a GPS, but check out the contour interval )