From its original conception as a military project, gps (global positioning system) can now be applied for both military and civilian use and is now widely recognized as a dual-use technology. In the last decade and a half we have seen this technology become more accessible to the average consumer, which can be witnessed with the ever-increasing number of portable handheld gps devices, as well as on-board car gps navigation systems that are either optional on purchase, or a standard feature on new cars. Marine navigators find this development to be especially significant, and are now able to take advantage of the digitally precise velocity and orientation measurements that marine gps systems are known to provide as a result of this increased accessibility. These specialized marine units are available in a variety of sizes ranging from portable handhelds all the way to large, station-mounted fixtures. With so many options available for marine navigation systems, choosing the ideal one can become a headache. There are certain identifiable differences in how various gps navigation systems will perform in certain situations. If you are a casual fisherman, a hobbyist that prefers to kayak in area waters, or prefer to navigate smaller boats close to shore or in a lake, a portable marine gps handheld will typically suffice. Your choice of model should be waterproofed as mobile versions of these gps systems have a tendency to take even more punishment than the average gadget you’d find lying around in your pant pockets. Finding a handheld gps device geared specifically toward the marine market can also be a challenge, although most if them come pre-loaded with marine chart software or at least allow you to download it later. Using the unit at night will require a high-contrast display and back-lighting. Although there is a certain convenience in being able to take them anywhere, these are not full-fledged navigation systems and will leave sorely lacking in features if you were to use this as your main navigation tool on larger boats and longer trips. Fixed-mounted navigation systems are bigger with larger screens and are designed to be permanently affixed to your boat’s navigation station. These are generally ideal for people who cover larger distances in their boat going from port to port such as fisherman who prefer doing their work further offshore. With these larger scale marine gps systems ease of use can become an issue. Defining your needs (and managing the impact to your wallet) becomes even more important as you will have to consider keeping or losing such features like MOB functions (Man Overboard) and navigate-to-track functions. At this point, the unit’s size will affect your choice of location for installation. Even larger boats may not have enough space to accommodate larger units.