[share_ebook] GPS for Dummies

图书介绍

As you may have guessed from the title, this book is about GPS (the satellite-based Global Positioning System) and maps; digital maps to be exact. I remember back in 1989 when Magellan introduced the first handheld GPS receiver, the NAV 1000. (Don’t worry. This isn’t going to be one of those “I used to walk 20 miles to school in the snow when I was your age,” stories.) The NAV 1000 was the size of a brick, and weighed a little less than two pounds. It was single channel receiver, could only track four satellites, and just supported latitude and longitude coordinates. It could save 100 waypoints and you could have a single route with up to 10 waypoints. It cost $2,500. Fast forward to the present. Now I can go down to my neighborhood sporting goods store and buy a GPS receiver smaller than a small cell phone. It weighs a couple of ounces, can track up to 12 satellites, and on a good day tells me exactly where I’m located to within about 10 feet; and in several different coordinate systems by the way. It supports 500 waypoints and 20 routes, with 125 waypoints apiece. Best of all it costs around $100.