Having Fun with GPS
Almost everyone has heard of the Global-Positioning System by now, and many radio hobbyists own a handheld GPS receiver. For the uninitiated, the GPS system works with a network of 24 satellites orbiting some 12,500 miles up in the sky. Each one has an atomic clock to set the precise timing that is part of the math used by a land-based a GPS receiver to triangulate its location on the face of the earth. GPS satellites continuously transmit signals and data. Those signals are picked up by GPS receivers, with up to 12 satellites being received simultaneously. A calculator in the GPS receiver crunches the data, and shows it to us as latitude and longitude.
The GPS term for a set of latitude and longitude coordinates is waypoint. If you connect the waypoint dots, you have what’s called a route. As you move with a GPS in your hand, it generates a virtual breadcrumb trail called a track. Waypoints, routes and tracks can be saved in a GPS memory. Now you have the basic GPS vocabulary.
Got a Map in Your Hand?
When people want to know how much to spend on a GPS receiver, we ask if they want to see a map in their hand. Entry-level GPS receivers display basic geographic information: latitude, longitude, elevation, direction, and bearing.
They calculate the distance between points and estimate your arrival time. They will also have a screen that shows a graphic representation of the points you marked with the GPS, as if you had drawn a sketch, but that isn’t a scale map. For that, you have to spend more, and most GPS users think it’s worth the expense. Better quality GPS receivers come with a base map of North America, but with such a large area to cover, the maps don’t include much detail. Spend a little more, and you get map memory, up to 24mb, to upload more maps and a higher level of detail: city maps, topographic maps, and “points of interest” such as hotels restaurants, museums, and so on. Garmin and Magellan, perhaps the most popular makers of handheld GPS units, produce software for this purpose.
Although you will see maps on your PC screen during the process of uploading them to your GPS, they aren’t meant to compete with real desktop mapping software.
By Anton Ninno, N2RUD, and Jim Kuhl, N2STK
