The Global Positioning System (GPS) is a navigation system that uses satellites in space to provide location and time information to anyone with a GPS receiver. There are 24 GPS satellites orbiting the earth in such a way that eight can be seen simultaneously anytime, from almost any point on the earth.
Despite its military origins, GPS is used extensively by civilians around the world. There are many uses for the system: fleet tracking, navigation systems, and even GPS watches for runners to know how far they have run. However, one of the most important uses of a GPS is to allow users to keep track of where they are on hikes or other outdoor expeditions. Buyers looking for an outdoor GPS receiver should know the different features to look for. After choosing the right outdoor GPS, buyers should know where to purchase it conveniently.
Feature #1: Map CapabilityUnlike mobile phones that require a data connection to download maps, map capable GPS receivers can work well without a data connection. Most GPS manufacturers provide detailed location maps that buyers can purchase at extra cost. The maps are sold as a downloadable file, or on other media. They are then loaded onto the GPS receiver from a computer. After that, all the GPS receiver needs is the location. It is possible to use free and open maps with some devices, but this may not be as accurate as other maps. Most map capable receivers come preloaded with a set of basic maps. Though more detailed maps are available, these maps do indicate the location of major highways and railway lines.
Feature #2: Saving Waypoints (Markers)Many handheld outdoor GPS units allow users to save markers, also known as waypoints, along a route. There markers can be used in several ways. Users can follow a path back the same way they went forward, or they can head directly to a selected waypoint. This feature also makes it easy to find a location again.
Feature #3: Dust, Weather, and Water ResistanceOutdoor GPS receivers are meant to be used outdoors. Most units are dust and weather resistant. Some are sealed more thoroughly and are certified waterproof to IPX7 standards. This means that the GPS unit can work even after being in up to 3 feet of water for 30 minutes. If buyers are concerned about dropping a GPS unit into deep water, they can purchase GPS units that are designed to float on the surface when dropped into water.
Feature #4: CameraSome GPS models are equipped with a built-in camera. Though these cameras are usually not as capable or complex as dedicated cameras, they are capable of taking a snap if no other camera is available. The photos are usually geotagged automatically (location data is saved to the image), allowing users to quickly find out where they captured an image.
Feature #5: High Sensitivity ReceiverBuyers who intend to use their GPS unit in locations where a clear view of the sky is not viable, such as in a forest or a city with tall skyscrapers, should consider a unit with a high sensitivity receiver. High sensitivity receivers are designed to integrate incoming GPS signals upto 1,000 times longer than conventional receivers. In situations where GPS signals are strong, this allows them to lock onto the satellites faster. In situations where the signals are weak, it allows the unit to lock on, where other units would have failed.
Feature #6: Patch or Quad Helix AntennaPatch antennas and quad helix antennas are two different types of antenna that achieve the same purpose: to increase a GPS receiver's sensitivity. Quad helix antennas can receive signals lower in the horizon better than patch antennas. This may be useful in situations where the GPS unit is used indoors. The signals from the ceiling are usually weak, but signals from windows can be received. However, the very fact that patch antennas do not use signals low in the horizon could increase their accuracy when used outdoors. In real life situations, both types of antenna work equally well outdoors.
Feature #7: CompassEven the simplest outdoor GPS unit features a compass. This is usually a simple compass that can only be used when the user is moving. Some units feature a more capable "three-axis tilt compensated electronic compass". This type works even when users are standing still. It can also be used accurately even if the GPS receiver is not held level to the ground.
Feature #8: Onboard Barometric AltimeterA barometric altimeter is a device that correctly measures elevation using changes in atmospheric pressure. Used in conjunction with a map, an altimeter can verify a user's location. The elevation reading of a barometric altimeter is more accurate than that of a GPS receiver. GPS units with onboard barometric altimeters give users more accurate altitude reading and can also be used to monitor the weather.
Feature #9: Geocaching FeaturesGeocaching is a sort of treasure hunt that was developed in the early part of this century. A "cache" filled with small prizes is hidden in a location. A GPS unit is used to take the coordinates, which are then uploaded to a geocaching listing service. Others can view the listings and set out on a hunt to find the cache with their own GPS unit. Once found, an item can be removed, but is usually replaced with another item of equal value. Some high end GPS devices now have features designed specifically for geocaching.
Feature #10: The Number of ChannelsGPS receivers are often described by the number of channels they have. This number refers to how many satellites the unit can monitor simultaneously. The first GPS receivers had only four or five channels. Today, GPS units are available with as many as 66 channels. GPS receivers with more channels can pinpoint location faster.
Feature #11: External Antenna JackModern GPS receivers are very sensitive, and in most cases there is no need to use an external antenna. However, there are times when a GPS does not lock onto satellites from within a moving vehicle, or a loaded backpack. There are also areas, such as in forests, where a clear view of the sky is not easy to find. External antennas can help in these situations.
Buying Outdoor GPS Units on eBayBuyers looking for outdoor GPS units online can find many models to choose from on eBay. To quickly locate a model with a particular feature, buyers can simply enter a phrase into the search bar on any eBay web page. For example, a search for "outdoor gps geocaching" lists the outdoor GPS units with geocaching features available on eBay. You can also browse deals on eBay for other electronics.
If a list of results is too long to be useful, buyers can narrow down the results by choosing from various criteria including the brand of the GPS receiver, its features, and the number of channels it has. Before committing to a purchase, buyers should review a seller's return or exchange policy. They should also ask a seller any questions they may have about a GPS unit. This ensures a smooth transaction and the possibility of a return in case the GPS is not as expected.
The "Global Positioning System" was originally developed by the military, but is now also used by millions of consumers around the world. It consists of a system of 24 satellites orbiting the Earth. With a GPS receiver, users can quickly pinpoint their location anywhere on Earth. All it needs is a clear view of the sky to lock onto at least four GPS satellites.
The GPS has many applications, including navigation systems in vehicles, tracking devices, and cartography. It has been used, ever since it was first developed, to help users navigate outdoors. Outdoor GPS units are designed for rough use and have many features, including higher sensitivity receivers, electronic compasses, and map capability, and others. Buyers should understand what each feature does before purchasing a unit. Outdoor GPS units can easily be found online on eBay.