7 Best GPS Units | March 2017
- rugged, crack-resistant design
- waterproof casing
- perfect for outdoor expeditions
- runs on windows 8 os
- can also play cds and dvds
- accepts up to a 32-gb memory card
- capable of fast map transfers
- able to share information between units
- touchscreen display
- very well reviewed by owners
- free lifetime updates
- good value with trusted garmin maps
What Exactly Is GPS?
Today, satellites are integral to the smooth operating of almost every industry, but as recently as forty years ago, they were predominantly used by the military. Global Positioning Systems (GPS), which are entirely dependent on satellites, were originally only available to the military, but the government gave the public access to this technology in the 1980s. GPS is made up of 24 satellites that the U.S. Department of Defense put into orbit in the late 1980s and early 1990s.
GPS, as we know it today, is the culmination of several previous systems, many of which suffered from a major issue; weather interference. Today, the satellites in orbit function under any weather conditions. The satellites go around the earth two times a day, following a specific orbit, and send information to GPS receivers on the ground.
Based on the time stamp of when the satellite sent the information, and the moment it arrived at the receiver, the latter knows exactly how far away the satellite is. The receiver then considers the distance measurements sent from the other satellites (it must be in communication with at least three to function properly), and using all of this information, it can locate where the GPS user is. When in contact with three satellites, a GPS is capable of producing a 2D location for a user. When in contact with at least four satellites, it can offer a 3D location, adding in altitude.
After a GPS has determined the receiver's location, it can determine other pieces of data, like the user's speed, the distance to their destination, and their bearing. GPS does all of this by emitting a low power radio signal that can go through glass, plastic and clouds. In terms of frequency interference issues, GPS has few. Its signal cannot, however, travel through very thick solid objects like buildings, which is why users often lose their GPS signal when they drive through tunnels.
What To Look For In A GPS Unit
While original GPS units were designed for military personnel, who are well-versed in jargon relating to longitude, latitude, and other distance markers, newer units are designed with the civilian in mind. Some, for example, use landmarks to help you know when to turn or stop. This addition might be especially helpful for women since studies suggest that they have great visual memory, and are better at navigating a city based on sites than geographical information.
Travel photographers, particularly those who spend time in open nature, can benefit from a GPS unit that attaches to a camera and adds geotags to images. People who go on hikes, camping trips, and other adventures that take them away from luxuries like electrical outlets and Wi-Fi need a unit with a long battery life, so they don't get lost in the wilderness with a dead GPS. Adventurers usually have to carry a lot of gear and can't hold a GPS unit, so they should look for one that can be worn like a watch. If your GPS unit is primarily for outdoor use, make sure it is ruggedly built and water-resistant.
Some GPS units boast a large memory of up to 4 gigabytes, so they can save your maps and routes. One of the top causes of car accidents in America is a distraction from an electric device. If you're purchasing a GPS unit for your car, look for one with a built-in microphone so you can speak your destination to it rather than punch it in with your hands.
The History Of GPS
The first manmade satellite, Sputnik 1, was placed in orbit in 1957 by the Soviet Union. Soon after, two physicists at Johns Hopkin's Applied Physics Laboratory named George Weiffenbach and William Guier realized that, based on the Doppler effect, they were able to determine Sputnik's location. The two were soon given access to one of the first commercial computers, the UNIVAC, so they could further their research on the concept. Weiffenbach and Guier eventually discovered how they could determine the location of the signal receiver, which spurred the creation of Transit, the first satellite-based navigation system.
Transit was originally used by the Navy in the 1960s. It consisted of just five satellites and sent location information to the user every hour. In 1967, the U.S. Navy improved on Transit and it was eventually replaced by Timation, which utilized accurate atomic clocks in space. Timation allowed its users to know what time the satellites sent out information, making it possible to determine a receivers exact location at any time. In 1973, the government started launching a series of 11 satellites that would be the beginning of the NAVSTAR global positioning system.
In 1983, a Korean passenger jet flying from New York City to Seoul, South Korea was shot down by the USSR, after it accidentally veered from its path and strayed too close to their borders. The USSR claimed they believed the plane was on a spy mission. This not only spurred severe anti-Soviet sentiments in the United States but also encouraged the U.S. government to make GPS systems available to civilians. Their hope was that all forms of transportation, from shipping and cargo jets to commuter boats, would be constantly aware of their location, to avoid accidentally moving into restricted areas.