Dead Reckoning--or DR as navigators sometimes say--is dead simple. The reasoning behind is this "If I go in such-and-such a direction for some known period of time, and if I know my traveling speed, I can deduce where I am. Put another way: The distance I travel is equal to time I travel multiplied by the speed at which I travel. Distance equals speed times time.
I won't get into the nitty gritty details of dead reckoning here, because I've covered that in my online navigation course.
Also, look on my land navigation web site, for detailed, yet basic information about dead reckoning.
DR navigation has been widely used for centuries. Let's get into our time machine, and head to August 3, 1492. We're in Spain, and one Christopher Columbus is about to lead an expedition westward into the open seas to find a western route to southern and eastern Asia, known as the Indies. Columbus knew the earth was round, and going west to get east made perfect sense.
Did he have a proper nautical chart that depicted where he'd be traveling? Of course not. All he had was a compass. Okay, he might been able to use the stars a bit to figure out his position, but from what I read Columbus was lousy at celestial navigation. But he WAS an excellent DR man. He knew that he'd better keep up with distance and direction traveled if he wanted to maintain a decent hope of getting back to where he started.
So, on that fateful day, he left the broad baseline of the European Coast and headed into uncharted waters, with only a compass and his brain to guide him.
Long story short, he faithfully plotted his DR course as he sailed westward. After a time, he didn't have clue where he was. When he found Cuba, he thought he was in China, about 7,500 nautical miles away. Nevertheless, he used his plotted course, reversed position, and sailed back home, well, to Portugal, but that's another story. At least, he made it.
Like Columbus, you can also find your way through unknown wilderness (unknown to you, at least) using only a compass, and still make it back very close to your starting point.
To video this being done, I went to one of the wildest places in Florida, the Big Cypress Swamp's Fakahatchee Strand. We left the Jeep on the side of the road, walked all though the swamp with no map, only a compass, and, like Columbus, made it back.
Anybody can learn dead reckoning to help them find their way, map or no map. Check out the video: