GPS seems to have come out of nowhere. There was no progression like eight-track tape to cassette to CD to MP3 player. One day we were driving around clueless of where we were, struggling with roadmaps bought at gas stations that couldn't be folded back neatly once opened, and - suddenly - there was an amiable female voice coming out of the dashboard offering directions to our destinations and showing no signs of impatience when we made wrong turns. Actually, GPS is based on simple ideas that have been around for centuries, but their implementation had to wait until the required technologies matured and came together. This book discusses these principles, technologies, and how GPS came to be developed. The only prerequisite for this book is curiosity about a technology that has insinuated itself into our lives in a way that we can't imagine how we ever lived without it.