Navigation 
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GPS Land Navigation by Michael Ferguson, et al
Navigation using sticks, stones and the stars
US ARMY FM 3-25.26 - Map Reading and Land Navigation
Caution: Even though the following excerpt from Jeff Hurn's book of a few years ago is optimistic, as it should be with the development of the Global Positioning technology, many amateurs get themselves into serious trouble (and some die) because they mistakenly assume that GPS technology can be substituted for basic navigational skills.
GPS, A GUIDE TO THE NEXT UTILITY
"Probably right from the time man got up on his hind legs and started to wander around the earth he's been looking for some simple way to figure out where he was and where he was going. "It's such a basic problem you'd think we'd have come up with something that really works. But right up until today every system has had problems. Early travelers just marked their trails with piles of stones. But that only works right around your own camp. And what happens when snow falls or when rain washes out the markers? "When man started to explore the oceans, the problems got even worse because there was no place to pile up the stones. And no landmarks to refer to. The only thing you could count on were the stars. Unfortunately, the stars are so far away they look pretty much the same no matter where you are. So the only way to use them is to make very careful measurements. And of course these measurements can only be made at night--and only on clear nights. "Even with the best instruments, celestial navigation can really only tell you approximately where you are, give or take maybe a mile. And sometimes that isn't good enough, especially when you try to find a harbor at night. "Modern man with all his gadgetry has tried a few tricky new systems, but even they have their problem. If you're a sailor you've probably heard of LORAN and DECCA. They are a radio based system that's pretty good for coastal waters where there are LORAN and DECCA chains. But they don't cover much of the rest of the earth and their accuracy varies depending on electrical interference and geographic variation. Another new system that uses satellites like GPS is called the Transit System or "Sat-Nav". Unfortunately, the satellites it uses are in very low orbit and there aren't very many of them, so you don't get a fix very often. And since the system is based on low frequency Doppler measurements, even small movements at the receiving end can cause significant errors in position. "Finally, someone got fed up and said, "That's it! That someone was the U.S. Department of Defense. They really need to know where things are and they've go the kind of money it takes to do the system right. So they came up with something called the Global Positioning System or "GPS". It's based on a constellation of 24 satellites orbiting the earth at a very high altitude. In a way, you could think of them as "man-made stars" to replace the stars that we've traditionally used for navigation. "The satellites are high enough that they can avoid the problems encountered by land based systems and they use technology accurate enough to really give pinpoint positions anywhere in the world, 24 hours a day. In actual use [except during the implementation of Selective Availability (SA)], people are getting measurements better than the width of an average street. And in "differential" mode surveyors are using GPS to measure down to [5mm]. "The new utility. But what's most exciting is its potential. With today's integrated circuit technology, GPS receivers are fast becoming small enough and cheap enough to be carried by just about anyone. That means that everyone will have the ability to know exactly where they are, all the time. Finally, one of man's basic needs will be fulfilled. This new service will become as basic as the telephone. Indeed, a "new utility." "The applications are almost limitless. Some are obvious: Delivery vehicles will be able to pinpoint destinations. [UPS, FedEx, etc. currently track parcels with GPS.] Emergency vehicles will be more prompt. And of course, cars will have electronic maps that will instantly show you the way to any destination. Other uses will follow. Since the system can locate things in three dimensions it will work for aircraft as well. In fact, GPS is thought by many to be the best (and cheapest) way to design a fool-proof air collision avoidance system. And right now work is progressing on very accurate zero-visibility landing systems. "But that's Just the start. GPS really allows every square meter of the earth's surface to have a unique address. That means that whole new ways of organizing our work and play are possible. Imagine a future when the phone book is no longer a paper book but instead a computer database in the memory of your computer. And instead of just listing phone numbers and addresses the book also stores the exact GPS location of everything. Then when you're looking for a Chinese restaurant, your computer could search through the phone database, find the location of the nearest Chinese restaurants to your current location and direct you to your choice immediately. No more aimless hunting. No more wasted driving. "This new utility would give the world a new "international standard" for defining locations and distances and it would allow nations to monitor and use natural resources more efficiently than ever before".
© Copyright 2007 - Samuel J. Wormley
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