# Tag Info

39

This map (and the Wikipedia article) will explain why you don't have a problem (in the UK, I'm guessing), but others do, elsewhere. In the UK, you can ignore it at the moment, but you need to understand WHY you're ignoring it :) As an aside, compare this with the declination in 1872... Then, the declination error in the UK would have been between 20 and ...

32

Compasses are good equipment both spelunking and diving. Even the deepest cave you could go to is still near the earth's surface, geologically speaking. The earth's magnetic field is also essentially the same under water as above. If you are using a compass, what you need to be aware of is nearby magnets and large sources of iron. So if you were exploring ...

23

This depends highly on your location. Contrary to popular belief, the difference between the magnetic pole and the geographic pole is not the only reason for declination. As a matter of fact, the magnetic poles are simply defined as the points where the magnetic field points vertically. This is not the same as the pole of a anyway non-existing earth-magnet. ...

21

Where your magnetic compass points can be quite far away from the north shown on your map For example, on the line marked 30, your compass would point 30 degrees away from true north.

15

Magnetic pole The distance from the rotational north pole varies over time -source By the time you read this, the north magnetic pole could be half the circumference of the planet away from the true (i.e. rotational) north pole. Thats over 20,000 km apart. It has been in the past. See magnetic pole reversal and rate of transition. Declination More ...

14

The distance between the magnetic north and geographic north poles is not important for navigation purposes. What matters is the angle between them, which is called the magnetic variation or magnetic declination. The magnetic variation varies depending on where you are on earth, and also changes slightly from year to year. In Pittsburgh, Pennsylvania, ...

14

They're absolutely NOT the same thing. The distance varies. But it's about 500 miles. (http://www.livescience.com/41955-north-pole.html) Since its discovery in 1831, the magnetic North Pole has been around Canada’s Ellesmere Island, about 500 miles (800 kilometers) from the geographic North Pole. https://en.wikipedia.org/wiki/True_north

13

According to this site there are only a few things that can go wrong with your compass: Mechanically, it can become hard to read because of a cracked dome or contaminated fluid; it can leak, causing a bubble in the fluid which, if allowed to grow, will interfere with damping of the dial; or it can become “sticky,” a condition that prevents the card from ...

12

There are several ways to determine true north, especially when you have a map and compass: Competent maps, like most intended for backcountry hiking, will have the magnetic declination marked. This is usually in one of the corners. Take a look at any USGS topo map, for example. The compass will tell you the direction to magnetic north, and the map tells ...

10

Olin Lathrop's very good answer to the question you reference basically already contains most of the information needed also your gut feeling about the topic is quite right. So let's look at it in a bit more general way: Keeping your compass declination in mind gets the more important, the closer you are to one of the magnetic poles, the more you travel ...

10

What you describe is exactly how it was done: Accurate measurement of distances and angles Obviously, measuring distances on flat ground is relatively straightforward: you use a known length measurement (perhaps a robe marked at known intervals); and to measure the distance to a distant point, use two points and a bit of geometry (Pythagoras is helpful ...

9

While Rory Alsop's answer points exactly to the method followed by cartographers and geologists before the invention of GPS and other modern techniques, I'd like to make a point that it was done with an assumption that they knew what altitude they are at and when you stand at planar location located from a mountain at a known distance and you can figure out ...

6

As others have said the importance depends on your location. In the UK & Europe the correction is quite small, approx 2-3 degrees and can therefore mostly be ignored. Compared to parts of the US where the correction can be at least 15 degrees. This is because the magnetic north pole lies somewhere in northern Canada, so the UK is relatively far away for ...

6

The topics of navigation and cartography are two sides of the same coin, and there are entire books written about each. It is interesting to study the history of cartography because it very graphically shows the corresponding improvements in navigation over time. In order to make an accurate map, you need to know first where you are making your ...

6

I picture would greatly help. However, I suspect you are looking at the lines on the part you manually rotate relative to the fixed base part. Good compasses have something you can rotate to set the offset for the local magnetic declination. For example, here in north-central Massachusetts, magnetic north is about 14½° left of true geodedic ...

6

There's cheap and there's too cheap! Remember - this is a tool you may be trusting with your life... For any kind of serious navigation you need a baseplate compass rather than the button type in your image. This is so you can take reliable bearings from your map to the land and back-bearings from the land to your map. Even the entry-level baseplate ...

5

Inexpensive compasses in general are fine. Even from a good brand the base models are not much more than the price of a few beers. Indeed in most cases these are all you ever need. However cheap button compasses are a bit suspect. To be fair it looks like that picture is 4 separate images photoshopped over a background so the fact that the indicated ...

5

Not discounting the existing answers which provide great perspectives. You don't really care where the North Pole is. It is not like there is only one or two, nor is like anything is stable. There are half a dozen north poles and most of them move around regularly and they move a lot (10s and 100s even 1,000s of miles/kilometers). Wandering of the ...

3

As the other answers point out using trigonometry you can determine the height of a distant peak. You can also use the same approach horizontally to determine the distance between two points. Provided that the length of one side of a triangle is known the other two sides can be calculated. Using a combination of these techniques any area can be divided into ...

2

We could get really complicated with this. But basically, magnetic north is a mostly fixed place on the surface of the earth. It's actually moving, but very slowly. Sometimes the map you have may have two compass circles on it. One inside the other. The inner circle identifies magnetic north, and the outer circle identified true north. In addition, the map ...

2

At night it is very easy to find true north using the stars (true south doesn't quite have an equivalent.) First identify Ursa Major, the Great Bear or Big Dipper. Then take the two stars at the end of it away from the handle, and follow the line they make for 5 times its length. The star you hit is Polaris. Head towards it and you are heading towards true ...

2

You need to do some research on the area that you are traveling on. Google maps or the NOAA maps using seaclearII.exe will allow you the ability to make a map guide, that you can annotate as you travel. mark off 100 yard and point to point track measurments. If you are going to dead recon from point to point on a river as an exercise or recreation you might ...

1

Consider the question in the terms of basic physics. Essentially, the magnetic pull of the earth and needle's magnet creates a torque on the compass (wheel / disk / needle etc. ) causing it to rotate. In an ideal compass, the torque meets only dampening resistance - you don't want the needle to move too quickly or you will get an oscillation while hunting ...

1

One of the primary techniques is the use of Dead Reckoning although the secrets of long distance Polynesian maritime navigation still remain a mystery despite huge evidence of their wayfinding ability. The easiest way for maritime navigators to map locations was to build on the predecessors knowledge through the use of the Periplus. It served the same ...

1

In the UK the prevailing wind blows from the south west and trees/ bushes grow away from the wind so assuming one can see a tree it should be easy to determine the other points of the compass. Elsewhere in the world it would be sensible to determine the direction of the prevailing wind prior to setting out.

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