subject: Features to Compare when Shopping for a GPS Unit [print this page] Features to Compare when Shopping for a GPS Unit
The technology behind the Global Positioning System (GPS) was created and tested by the U.S. Department of Defense (DOD) in the 1970s. But the concept behind it was based on an invention of our then mortal enemies, the Soviet Union. When the Soviets launched their first satellite, Sputnik, into space in November of 1957, scientists at the Massachusetts Institute of technology made a startling discovery.
What they found was that the strength of Sputnik's radio signal changed as it orbited the planet. As the satellite approached their position, the radio signal grew in strength, and as it moved away, it grew weaker. With a little quick math, the scientists were able to determine the satellite's exact orbit. They also postulated that the satellite could be used to pinpoint the location of an object on the ground as long as it had some kind of device that could receive the signal from the orbiting satellite.
Twenty-one years later, the DOD launched the Navigation System with Timing and Ranging or NAVSTAR. The program originally consisted of 11 small satellites that were designed for military use. The first transmitters were installed at US military facilities around the world and were used to test the accuracy of the first satellites. The results were compelling enough to justify the launching of an additional seven satellites over the next five years.
In 1983, the government decided to make the new technology available to the public. Like any new technology, however, GPS was extremely expensive and fairly unreliable. The first devices could not tell civilians where they were with any degree of accuracy.
Even the best, most accurate devices could only "pin point" the user's location to within 100 meters. This meant that GPS was completely and utterly useless when it came to driving directions. Though they were used by commercial fishermen to give them a rough idea of where they were.
What most consumers did not know is that the military had restrictions that limited the accuracy of these devices to 100 meters for civilian users. This selective availability was not deactivated until the year 2000. But when it was, a huge market for GPS units sprung up almost overnight.
With an average accuracy of 10 meters, today's devices can be used for everything from driving directions to keeping track of the family pet. In this article we will discuss a few of the most important GPS features.
Often called portable navigation devices, all GPS devices for the family car come complete with pre-loaded maps and automatic rerouting, if you happen to miss an exit or a turn. Depending on your needs, however, you may require a few additional features. Here are just a few that you should consider when you are comparing models.
Screen Size
We've reviewed GPS devices with screens that range from 2.5 to 7 inches. Though all of them worked quite well, the smaller screens can be difficult to see and their tiny touch-screen buttons makes it much harder to enter the right address.
On the other side, the larger units can be quite heavy and they may obstruct your view of the road when they are mounted to the windshield. Our advice to you is to select a unit with at least a 4-inch screen. It will be much easier to read and to use and it will not obstruct you view of the road.
Spoken Street Names
Most modern GPS units will tell you when to turn, but they will not tell you the specific highway, route, or street name to look for. They will simply say "right turn" or "left turn" ahead. But the most expensive units will give you the actual street name before you have to turn.
This can come in handy when driving in busy, unfamiliar areas, like the city, where intersections are closer together and knowing the street name can save you from taking a wrong turn. Have you ever made a wrong turn in the city at rush hour? It can take twenty minutes to get back to where you were. Trust us: this feature is easily worth the extra fifty bucks.
Traffic Reports in Real-Time
GPS devices with traffic information will tell you when there is a detour, an accident, or a slowdown ahead. They will also provide you with additional routes so that you can avoid them. Unfortunately, these updates are only available in certain cities, and even then you will have to pay a hefty subscription fee. Users may also have to purchase an additional receiver that costs about a hundred dollars. Still, the service is well worth it for people who spend an hour or more in traffic each day.
Detour Feature
Whenever you see a detour sign, depressing the manual detour button will provide an alternative route almost instantly. Some units let the user select a number of options based on the distance it takes to avoid the detour. Most new models offer the detour button as a standard feature.
Mounting
Most GPS devices are mounted to the windshield with a large and powerful suction cup. But since some states, like Minnesota, prohibit these mounts for fear of visual obstruction, manufacturers have begun offering different mounting options. We like the bean bag mount, which is a unit that simply sits on the dashboard. These devices are a cinch to install and they stay in place. There are also models that adhere directly to the dash with a kind of self-adhesive disk. These units are every bit as secure as the original suction cup models.
Be sure to take these ideas and suggestions into account before you decide on the GPS unit that's right for you.
