no trader, you do not need to subscribe to any service. GPS works by, a series of satellites transmit their position data (almanac data) and a time signal to a receiever on the Earth. Because the receiver can identify each signal, identify which satellite it came from and the time the signal was transmitted, it can resolve the time errors to derive an accurate position. The time signals may be un-unencrypted for civilian use, or encrypted for mulitary users. Of course, the Americans were the first, but there are currently at least two different systems in orbit around the Earth, one US (NAVSTAR) and one Russian (GLONASS). You can buy commercial receivers for one/both systems. I do believe there is a unit that simultaneously receives both signals and does its own error checking, just in case someone is playing with the information! I also thought the French had/were looking to launch a system, but I have not been able to confirm that in the time it has taken me to type this. For more information: http://www.garmin.com/aboutGPS/ http://www.dkart.ru/gps.htm and many many more..... All you need to do is buy a receiver to intercept and process the time and almanac data, and a method of displaying the processed information. The unit you are looking to purchase does all (and more) for you. Hope this helps. wabbit :D

As I mentioned you need a GPS receiver. Your current PDA is not fitted with one. You can buy them to plug into your PDA, but you might find it better just to go out and buy an integrated model. When you buy the Garmin and/or NavMan GPS enabled PDA you get a display system with it. You can buy other display systems if you like. You need to see all of the features and functions, chose which ones are important to you, then buy the compatable software that best suits your needs. You should be able to purchase at reasonable prices the add-in sections for the part of the world where you want to explore. These could include details of every petrol station, pub, hotel and motel in the region, tourist sites, historical sites etc etc. In Australia, you can buy "survival packs" detailing the locations of many places where you can get water, fuel and first-aid in the Australian deserts. There are literally hundreds of different "navigation" software packages that you can buy, for standalone systems, integrated systems, PDA, PC based etc etc. Remember these packages only display the position and time information AFTER it has been decoded by the GPS receiver in the first place! Hope this helps. wabbit :D