DEFINE NORTH

I thought so.

So moss always grows on the south side of trees.

..... in my hemisphere.

In the northern Hemisphere, I look for Polaris. Polaris is not hard to find. During the day, if I had two horizons, I'd mark sunrise and sunset and take the right perpendicular to sunset. This one could be pretty exact, but in practice no better than finding Polaris. Compass is OK but it points to magnetic North. Moss on north side of tree is pretty good if you know something about moss and trees, and your in a deciduous forest. Finally I'd depend on my gut, I don't think it is instinct I think it is my subconscious seeing something that my conscious does---and in general it is pretty good (+/- a sector).

Over the longer period, you could note the change in solar noon, ir if you knew solar noon exactly and had an accurate clock, you'd have North. There's a boy scout process to find north based upon shadow at two different times, but this assumes an accurate timer.

Moreover, if you knew solar noon (Longitude) and had the data you could note declination and have your longitude. This is pretty much the basis for celestrial navigation (measuring the complement of this angle--the one with Polaris also gives longitude, but not Latitude).

GPS---wonderful system, but don't count on it (Batteries Die). Works on the triangulation between referenced sources. There are fourtysomeodd satellites in LEL that's have (as part of their purpose broadcasting, their name, and position digitally. When a ground based receiver, yes that little battery hog in your hand, receives this information from three or more of these satellites, it's little brain performs a subroutine that calculates a position based upon triangulation (it a little trick from trigonometry---you know triangle based. A note---as the little battery hog starts picking up additional satellites (or closer ones) it starts getting really accurate (mine claims at times +/- 35 feet--but I don't trust it).

Finally, a compass and a topo is the best. Once you've found reference points you orient your map to the local magnetic North, spot an reccoinoiter position and call in the HE.

Rap

Eorl said

That wouldn't be true if you used the Australian Corrected Map of the World UpsideDown Map Page

Rap

makes sense to me.

The most interesting thing about that map orientation is how it has extended out to the solar system (and the rest of the universe) You never see Jupiter shown with the Red Spot on top.

Walk around on the Earth's surface in an organised search pattern, with a magnetised knitting needle tied onto the end of a piece of string, so that the needle is laying in a horizontal position.
Keep looking at the needle, and when you accidentally pass over "Magnetic North" the needle will point downwards. True North may then be located by pacing 1200 steps (for a person with an average stride of 22 inches) to the left. Or is it the right?

Wouldn't it be 1200 steps north? :wink:

Similarly, walk around on the landmass that is North America, and look for clues.
If one notices the Confederate flag in abundance, one should turn in the opposite direction and keep walking in a straight line.
To confirm that one is heading in the right direction, keep an eye out for Mounties, and Pine Trees. These are good signs.
After passing several Canadians and a lot of snow, keep on walking until one notices a group of huts with "North Pole Research Station" written on them. One is now VERY close.
Ask inside one of huts.

Ellpus , if youre not at tea. SO far your answer is closest tothe definition "North". The process is tedious and is what defines the azimuth N by exactitude (We make maps that we wish people to confide in)
One needs some equipment. An alidade, an optical plummet transit, or and Electronic distance measuring transit EDM.
One must go out on a clear night and find POLARIS. We set up our instruments with Polaris at the center and our plummet reference at 90 to the horizontal. SO we now have an instrument with polaris in the bullseye and we wait for two other stars (Delta and Mizar , which is occulting ALcor) We need star manuals and flashlights, and we wait, and wait, until at the magic moment in time when all three stars are perfectly vertically aligned. That is true North. So when we use a map, we must pay some due to the poor schmucks who got that duty before say 1985 when the basic GPS system was working.

In the SOuthern Hemisphere, finding S is a bit trickier because it involves the vertical columation (its what we call the whole multiple star alignment thing) of a series of rather obscure constellations (Octans) and the star canopus. There is only one true pole star and its polaris.

All this is something that the student learns, gets tested on, then forgets , because all semester theyve been using surveying GPS systems that, with all the software built in, are able to tell us where N is and give s accurate redaings of any spot on the surface within 1 cm > ( Those instruments used to cost about 20K, they now cost about 5K).
Most GPS's will as rap and others have said, give us accurate readings to at least a meter if the GPS is enabled for Wide Area or WAAS. GPS just integrates by polar coordinates using a complex algorithm the reference position, the GPS position, and your position as an unknown. There are about 24 satellites usable in the N hemisphere (I have to plead ignorance in the S because I dont do the surveying anymore). When we polar triangulate in the N, we require at least 8 satellites and, as its the US govt, they are usually taking satellites off line for military purposes and sometimes our waits are long.
Always have spare batteries or, in the case of our survey quality instruments we plug those into ourpower inverters since they can use a 120 AC driop circuit.

They will tell you N/S , your heading, your speed, the areas of your traverse, they will allow you to save your field data and ownload onto a base map.
The price we pay for accuracy in a surveying GPS , is speed. We may take readings for one spot that needs to be horizontally corrected by differential via a known base station. We can take up to an hour to get a single point of reference at +/- 0.01 cm accuracy. However, follow -on points speed up.
If we are dropped into an unknown area. GPS is the only way to go.

Yes, but I am always putting that "G..D.." devise down a stump somewhere and then forgetting where I put it. As a result I'm stumbling around in the woods for a half an hour trying to find it. A theodolite on a tripod is big and generally painted yellow, you can't miss it.

Maybe someone should invent a GPS locator so you always know the precise location of your GPS!

Oooh, I WANT one of these !

http://www.imtecgroup.com/gyro.htm

Would you mind letting me know where my definition of North went wrong? I am curious.

Brandon-your answer was , let us say, incomplete for a grade. Id have to ask you why wouldnt your concept work in an application? What about Chandler wobble and precession? do they affect anything?
The best answer of what is North, is how do we measure north .

Yes, the Earth wobbles a little as it rotates, but I was answering your question:


Was my answer incorrect?

It was incomplete and incorrect. The axis and North have a tangential correlation only

Okay. It's not something I know much about at all. Not sure what was incorrect about it, though. Looks like Websters has it wrong too.



Source

explain tangental. Are you saying that the axis isn't North? I agree about the precision, but because North isn't North, it appears that you're still looking for a benchmark North, instead of the nominal definition.

If so then one would in most places track the benchmarks and milestones. If so I'd get my topos and shoot one of each. They're aways down the road, but for Ohio I got a hellaview.

From those two azimuths, I got North to within 30 seconds., .

The alignment of stars is interesting, and I can see how it would work to account for the condition that Polaris is only the North Star temporarily.

Call me a luddite, but I still say the old ways are more reliable than GPS. In some future time where computers are everywhere, a man who can do long division will be considered sage.

Rap

Oh boy, the
" Heres what Webster calls it" defense.

I really expected more from you Brandon. You usually come up with really bright stuff.

My personal merits or demerits are irrelevant. You have said that my answer was merely wrong, and not in a very friendly way either. I see some indications, not conclusive, but indications, that there was at least some bit of truth in what I said. You are the undisputed expert, giving a quiz to us. The quiz is apparently supposed to be sort of fun. We don't know much about your subject. Under that circumstance, I find it hard to understand your absolute scorn for giving me the tiniest credit for an answer which seems to contain some truth.

Websters is not a good place to get one's science, but they are no fools, they are very accustomed to defining technical terms, and they have experts who check their work. This doesn't make their work competitive with real science, but it probably indicates that their definition is not absolute hogwash, which is sort of how you have described my entry into your quiz.

farmerman - Fun thread! :-) When you get around to it ...


If North is defined by how you measure it,
then does North cease to exist when it can't be measured (cloudy night,
or daylight blocking the stars?)

Maybe defining it in terms of something more universal ...

The gyroscope method (of detection) is highly accurate and works even in a cave two miles underground.