How many ways are there to find north and south. It turns out there are a lot. Most methods that take advantage of basic astronomy that allow you to find true north and south. These are methods that could come handy in a survival situation.
The picture above illustrates one of my favorites. It isn't taught as much because watches have gone digital and the method is seen by some as anachronistic because of this. The picture pokes a bit of fun at this because I borrowed a cellphone that had a "retro" watch face. The setup shown is northern hemisphere during standard time (it wasn't but it's just an example). The yellow line shows north.
If you've become lost the simplest recommended method is the Hug a tree approach. This prevents you from getting further lost and facilitates rescue. Navigation methods like the ones described here are a bit more advanced. Nonetheless they are worth practicing! They won't easily help you find a small site like a camp, but wide things like highways and major rivers are another matter.
This method is fast, portable, and reasonably accurate for these kinds of general methods. And even if you don't have an analog clock face, then you can draw one easily enough. It's not perfect (see below), but handy.
Cast a shadow across the watch face.
- In the northern hemisphere, align the hour hand to the shadow. You will now need to bisect an angle (find the halfway angle) between the hour hand and noon (or 1pm if you are on daylight savings time). The line running through the bisected angle will run true north-south. North will be the side of the line closest to 3 o'clock in the morning and 9 o'clock in the afternoon.
- In the southern hemisphere the approach is almost identical (it would be if you had a clock that runs anti-clockwise). In the southern hemisphere align noon (or 1pm if you are on daylight savings time) to the shadow. Bisect the angle to find the north-south line. North will be the side of the line before 12 in the morning and after 12 in the afternoon.
Some drawbacks include that you can easily be off the width of a timezone which is typically an hour but can vary. Knowing if you are close to a timezone boundary will help with this. It's also not supposed to very good if you are either too close (under 20°) or too far (more than 70°) from the equator.
There are several methods for using the Sun to find direction.
- Knowing that the Sun rises in the east and sets in the west. You can figure an east west line at sunrise or sunset. There will be some variation depending on the time of the year and length of day, but the Sun should be due east/west at 6 o'clock am/pm.
- "Shadow Tip" methods. These are described in detail in an article below. Basically, there are different ways to get an east-west line. The one that makes the most sense involves taking measurements on equal times before and after mid-day. While I haven't tried the others, I have a hard time believing that drawing a line between two shadow tips at 20 minute intervals around 7am will result in an east-west line. (But perhaps I missed something.)
Locating direction using stars can be accomplished by several methods.
- Use sticks to track the rise and set of different obvious stars. This is a method that was believed to be used by the ancient Egyptians to layout the pyramids. The line between the rise and set of a bright star should be an east-west line. Of course, this requires you stay put for a while.
- Locate a landmark beneath the pole,
- In the northern hemisphere, this is beneath the north star located by using the pointers in the big dipper. See the Astronomers badge.
- In the southern hemisphere there is no easily visible pole star so it's trickier. You need to find the long axis of the Southern Cross (Crux), the pointers in Centauri, and Achernar in Eriandus. These intersect over the south pole. Some of the diagrams on the web don't show the pointers and this intersection. For more detail see here. Also, be wary as there are false pointers, a false cross, and the diamond cross to confuse you. For more see here. (As I've never been this far south, I'd love to hear from someone who's actually done this. Musca where are you?)
- This is another approximate method. Basically, the phase of the Moon will tell you the location of the Sun. Additionally, if the Moon rises before the Sun sets it is trailing the Sun and the bright side will point approximately west. If the Moon rises after midnight it is leading the Sun and the bright side will point approximately east.
- Another interesting looking trick is described as a "finger of shadows" on a nearly full Moon to point due north. It can be found here. I may be wrong but, this sounds overly wordy and colourful.
- The previous trick got me thinking about a crescent Moon. The line between the tips of the crescent should run approximately north-south. This makes sense if you consider that the Moon orbits close to the ecliptic (within about 5°) and will be illuminated from north to south.
Non-GPS software is available for a number of mobile phones and PDA's. I'm most familiar with Palm OS based tools, but I understand there are versions for other devices such as Windows mobile. Possibly the Blackberry and other devices? I'd love to see comments on recommendations.
- Sun Compass for Palm
- Sol! a Sun compass for the Palm
- A number of Pocket PC and Palm "Sun compass" products can be found at PocketGear.com.
- I wasn't kidding about backwards or reversed clocks. They are commonly available for left-handers or as novelties. One example see here. (It would be exceptional to see one with a 24 hour dial.)
- Surveyors used very accurate Solar compasses because magnetic compasses could often be thrown off by deposits of magnetic minerals. A photo of one can be found here.
- I recently saw design for an unusual clock called the "Bulb Dial" clock, here. It's sort of a minimalist and Rowland_Emett-ish at the same time. (Emett is known for his wacky art-inventions that were featured in the movie Chitty Chitty Bang Bang and regularly displayed at the Ontario Science Centre in "The Magical Machines of Rowland Emett").
- While I 'm not certain you can find north-south with it, a related find was instructions for a do it yourself Sextant using a CD case and Lego, here. (Careful about the sun filter).
- Earth dials are interesting and would make an interesting school or Scouting project. This Planetary Society article provides instructions on how to build one.
- For more information on these methods see this Wiki How To article. This covers many of the methods mentioned in more detail including using a digital SLR camera and a cell phone as well as the watch method, shadow stick, and star methods.
- Another explanation of the clock method with diagrams can be found here.
- Yet another explanation of several methods can be found here.
- The Planetary Society posted an article on Earth Dials (see below) with links that include a sites that calculates magnetic deviation for your locale and several links for teachers and kids including Astronomy with a Stick.