Handheld GPS devices can be used for tracking your location and itinerary whenever you are in the oudoors for your safety and convenience. They can provide you with accurate information about your exact position, elevation, topography, sights of interest, and other details. Portable GPS handheld systems are convenient to carry since they are small and lightweight.

In the past, all we had available was a compass and a map to help us figure our location. Now, with the era of portable GPS devices, you will never get lost even if you don’t have a compass and a map with you when you travel. Equipped with a handheld GPS device, you will never need to ask for directions again.

It is fairly easy to understand how the GPS unit works. Satellites transmit signals and the portable GPS units receive signals. There are 24 satellites that encompass the globe, and usually, you’ll have anywhere from five to twelve satellites in view of a GPS receiver anytime, anywhere. The GPS receiver gets signal from these satellites and calculates its own location based on its position to the satellites. If some of the satellites in view get blocked, or “shaded”, the receiver can simply use an alternate satellite to acquire its position fix.

GPS receiver knows when the satellite sends a signal and measures how long it took to receive the signal sent by the satellite. This enables the portable GPS receiver to calculate how far it is from any particular satellite.

Each satellite transmits data that gives its location and time. All satellites are synchronized to transmit at the same instant. Because the satellites distance to a given point on earth is different for each satellite, the time it takes the signal to reach the portable GPS device also varies depending on the device’s location.

Based on the time and satellite location information, which are both known, it is possible to calculate spheres of location on earth from each satellite. That is, at any point on the sphere, it takes the same time to receive the signal from a particular satellite. After four satellites have been “acquired” (seen) the GPS receiver can calculate its location (longitude and latitude) on earth. This position is based on where the four spheres intersect.

Although a GPS receiver needs at least four satellites to provide a three-dimensional (3D) fix, it can maintain a two-dimensional fix with just three satellites. A 3D fix includes latitude, longitute and altitude; a 2D fix provides just latitude and longitude.

The portable GPS then converts that data into a readable format, and displays it on your GPS device’s screen, for example, your location on a map. How accurate are they? Today most portable GPS units provide data with an accuracy of about 50 ft (+/-), but many do even better than that.

If you are looking to buy handheld gps navigation system, read more about GPS Handheld systems and How to choose the right GPS device for your needs?