Will compass work in Southern Hemisphere?

[Trail Bandit]

Nessmuk and DougPaul have covered most of the important stuff about compass navigation in high latitudes. There is a bit about the wandering of the magnetic poles at:
http://www.ngdc.noaa.gov/geomag/GeomagneticPoles.shtml
All this is even more fun if you happen to be in a moving vehicle (airplane) and make a turn. Airplanes usually bank into a turn to keep the force of gravity + the centrifugal forces perpendicular to the wings. The compass no longer deals with only the horizontal component but responds to the vertical part too in varying amounts depending on the angle of bank. Flying East along the Arctic coast from Barrow, AK I found that the compass would just spin wildly for numerous revolutions with even a small turn. As luck would have it, it was a relatively clear day and I could see the shoreline most of the time. The GPS was a a lot of help and worked flawlessly but as noted by others make sure you remember that the GPS is giving true north and the compass points to magnetic north (south). (Some GPS units can be set to read out magnetic degrees using the variation corrections that are in the unit's data base.) I have no idea how explorers, sailors, or anybody else found their way around before the days of radio, inertial, and GPS reference systems when there could be weeks or months when the sun and stars were not visible. Pilots of airplanes don't usually have the option of "Waiting until it clears off" to find home base. I am ashamed that I have never bothered to learn the "lost art" of navigating by the stars.

 

[Stan]

I have no idea how explorers, sailors, or anybody else found their way around before the days of radio, inertial, and GPS reference systems when there could be weeks or months when the sun and stars were not visible.

Overcast skies were not the only hindrance to celestial navigation but the persistence of the weather often revealed something about their location. Accurate time is essential to most of the navigation resources in the heavens. There are some exceptions.

The north star directs you to true north, within a couple degrees, and easily gives you latitude. In the northern hemisphere, the high point of the sun is always due south and can give you an approximation of latitude if you adjust to season. Early explorers were keen enough to understand this and to know the direction of sunrise and sunset on a seasonal basis. They probably observed that the tangent of the points of a new moon point south. The vertical line of the southern cross points south.

Explorers crossed oceans with this comparatively simple knowledge and once they approached land, their sensitivity to the color of the sea, prevailing winds, seabirds and other natural features helped them navigate towards a destination. They were sharp at identifying land features and once they approached land the lead line was in constant use.

Their power of perception probably rivaled that of birds, insects, fish and animals. I wonder which I'd prefer, the power of their perception or the power of today's technology.

Still, lots of ships were lost at sea or grounded but even today's technology hasn't prevented that.

Shackleton's 800 mile sea jouney for survival is a more contemporary example of remarkable celestial navigation with little more than primitive methods.

The first chapter of Nathaniel Bowditch' American Practical Navigator briefly describes the history of navigation. The Natural Navigator by Tristan Gooley is a fascinating book about "the rediscovered art of letting nature be your guide".

 

[Nessmuk]

The first chapter of Nathaniel Bowditch' American Practical Navigator briefly describes the history of navigation. The Natural Navigator by Tristan Gooley is a fascinating book about "the rediscovered art of letting nature be your guide".

The story of solving the longitude problem has been fascinating to me. Try googling for terms with "longitude problem", "longitude prize", and "John Harrison". When I was an Air Force navigator using celestial navigation, I kept in mind that a 4 second error in time could translate into as much as a mile of position error. I made it a point to know and compensate for the error rate of the EMP resistant mechanical watch I carried.

 

[Highcomm]

My wife and I will be going to Patagonia next week for ten days. From there we go to Antarctica for three weeks. Will be doing some hiking but just day stuff. Here is a question for all of you as I can't seem to find a straight answer on the Internet - does a compass work in the southern hemisphere? Will the magnetic needle still point north? This is not a huge issue for me but just wondering. Thanks for your help!

I just got back from my five week Patagonia/Antarctica trip last week. Just before leaving for the Antarctica segment of the trip, I did an experiment in the city of Ushuaia which is located on the southern tip of South America. It's latitude 54°48′south. I visited a local park that had a large decorative compass made out of stone. I used it to get my north, south, east, west bearings. Side by side I set up a North American compass, a global compass, and an iPhone compass. All three pointed in the exact same direction - north (see photo below). I mentioned my experiment to a guy I met from Australia. He said, "Of course they pointed north. A compass will point north unless you sitting on the South Pole..." As I mentioned in my previous post, this was not a huge issue for me but it was fun finding out the answer.

 

[Tom Rankin]

I mentioned my experiment to a guy I met from Australia. He said, "Of course they pointed north. A compass will point north unless you sitting on the South Pole..."

He's wrong. It points North everywhere. As others mentioned, it might be pointing DOWN at the South MAGNETIC Pole (not the Geographic Pole) but it will always point towards the North MAGNETIC Pole.

 

[DougPaul]

I mentioned my experiment to a guy I met from Australia. He said, "Of course they pointed north. A compass will point north unless you sitting on the South Pole..."

The comment is ambiguous since it doesn't specify magnetic South Pole or geographic South Pole.

* If you are at the geographic SP, then
- all geographic directions are North
- the S end of the compass needle will point at Australia (ie toward the magnetic SP) and the N end will point toward eastern South America.
* If you are at the magnetic SP, the magnetic field will be predominantly vertical and the compass (if it works at all) can point in any direction following small anomalies in the magnetic field.

* One can make similar observations when near the magnetic NP.

Background info:
The magnetic SP is currently located just offshore of Antarctica in the direction of eastern Australia, about 1800 miles from the geographic SP and the magnetic NP is currently offshore N of Canada, about 380 miles from the geographic NP. Both have moved hundreds of miles in the last four centuries.
http://modernsurvivalblog.com/pole-shift-2/pole-shift-north-races-south-crawls/
http://www.ngdc.noaa.gov/geomag/GeomagneticPoles.shtml

Doug