GPS for Dummies.pdf - Engineering Surveyor

156Part III: Digital Mapping on Your ComputerFor this connectivity, you need a PC interface cable. It has a connector thatattaches to the GPS receiver on one end and an RS-232, 9-pin serial connectoron the other end to connect to your computer.Newer GPS receiver models support USB. If your GPS receiver supports bothserial and USB interfaces, use a USB cable for much faster communications.If you bought a GPS receiver that didn’t come with a cable and you can’t find acable to buy, you’re not necessarily completely out of luck. If you’re handy witha soldering iron, most GPS receiver manufacturer Web sites describe the pinoutconfigurations of their cables so you can make your own. The tricky partcan sometimes be finding the right connector for the GPS receiver becausemost connectors vary between manufacturers and models. A number of how-tosites on the Internet show you how to build your own cables and where to getthe connectors. Do a Web search for gps cable connector and the brand of yourGPS receiver to find different options.Some cables are designed to both power a GPS receiver from a cigarettelighter and to connect to a computer to send and receive data. These cablesare especially useful if you’re using your GPS receiver with a moving map programand a laptop. Just remember that you’ll also need to buy a dual, car cigarette-lighteradapter so you can plug in both your GPS receiver and laptopinto a single cigarette lighter.If you have a Garmin receiver, check out the Pfranc company for its qualityGarmin-compatible cables. Larry Berg started out making shareware Garmincable plugs, and his business grew. He now stocks a line of reasonably pricedcables for all Garmin models. Check out his Web site at www.pfranc.com.Understanding Ports and ProtocolsArgg. You track down the right cable you need. You plug one end into yourGPS receiver and the other into your computer. And nothing happens. Exactly.Nothing should happen because you need to be running some type of softwareon your computer that enables the two devices to talk to each other.Before I discuss interface software, however, I have to lay some groundwork.The programs designed to communicate with GPS receivers have one thing incommon: You need to specify certain communication parameters in both theprogram and the GPS receiver for the devices to successfully exchange data.If the settings aren’t correct, you may as well try to communicate with someonea thousand miles away by sending smoke signals through a telephoneline. Although setting the right communications parameters isn’t that difficult,it can be a bit confusing. This section guides you through the processand also gives you some tips on smoothing out some common problems thatyou may encounter, beginning with ports and their settings.