Don't buy this book! This book contains a fair number of typographical errors that tend to give it a 'sloppy' feel. Also, one analogy given in this book was apparently taken from GPS A Guide to the Next Utility by Jeff Hurn and published by Trimble Navigation in 1989, to whom the authors make no reference. It should also be noted that approximately half of this book is just made up of reprinted advertisments for different kinds of GPS equipment. To a few this may be useful, but it will quickly become obsolete. There are many other books that are much better. For a short, straight forward tutorial see the Trimble Navigation web site, and for an introductory level look at the uses of GPS for precise positioning see GPS for Land Surveyors by Jan Van Sickle.