...a sport that uses simple navigation techniques like map reading, piloting and dead reckoning. It's a little bit like sports car rallying on foot.

The essential technique of piloting is the triangulated fix: take compass bearings on distant objects which appear on your map, plot them, and where the lines cross is where you are. Dead reckoning is just the ability to estimate your position using your last known initial position and estimates of your course and speed. The calculations are done graphically. It's a lot easier than it sounds, actually. The skills you need are mostly gained from experience and common sense, and deliberately introducing error into your calculations so if you guess wrong your error is not likely to get you into trouble. For example, you deliberately steer upwind of your destination, so in case you miss it, you don't have to beat to windward to get back on course.

Celestial relies on the exact same methods, but you rely on precise measurements with a sextant and astronomical calculations. GPS also works the same way, but you're using radio waves, artificial stars, and all the thinking is done for you on a chip. All navigation is based on the Line of Position, a line on the chart which you know you are located somewhere on. When two LOPs cross, you have a fix (position). Three lines give you an idea of your possible error or uncertainty. Four allows you to completely disregard one observation and discard it if it contradicts the other three. And so on.

Did you read my post on "Penn's Woods" in "Off Topic" on 6/25/06?