| GPS stands for Global Positioning System and the | | | | 5 more control stations which would mean that |
| System refers to a network of satellites that | | | | each satellite will be seen by at least three of |
| orbit the earth and transmit information back | | | | them. |
| constantly. A handheld GPS receiver is a GPS | | | | The User |
| navigator unit that is highly portable and can | | | | The user in the system is each individual with their |
| receive information from the satellites so as to | | | | handheld GPS receiver. Users of handheld GPS |
| pinpoint certain locations on the ground, in the air, | | | | receivers can include hikers, boaters, pilots, |
| or on the water. | | | | fishermen, hunters, military personnel, or for |
| The 3 Parts of GPS | | | | Geocaching fun. Basically, they are useful for |
| GPS consists of three parts; space, control, and | | | | anyone that wants to know where exactly they |
| the user. Space refers to the satellites, control | | | | are at a given time or to know where they are |
| refers to the control stations on earth, and user is | | | | going to. |
| the person who operates the GPS. | | | | How Accurate is a GPS? |
| The Satellites | | | | Today's GPS receivers are more accurate than |
| Currently, there are 24 satellites orbiting the earth | | | | ever but they can not always be 100% accurate. |
| once every 12 hours. They were originally | | | | Common handheld GPS receivers can track your |
| launched by the US Department of Defence for | | | | position from about 3 to 15 metres but there are |
| military purposes but they are now also used for | | | | some errors that can affect the accuracy. A few |
| civilian use. A GPS receiver needs to lock into at | | | | of these errors are caused by the delay in signal |
| least three satellites to give a 2D location of | | | | as it passed through the layers in the |
| longitude and latitude and four or more satellites | | | | atmosphere, signals that are reflected off tall |
| to give a 3D location of longitude, latitude, and | | | | buildings or rocky mountains that increase the |
| altitude. | | | | time for the signal to reach the receiver, or the |
| When the GPS receiver's position has been | | | | number and position of the satellites relative to |
| determined, other measurements can be | | | | each other. |
| calculated like the speed the user is travelling, the | | | | What Features to Look for in a Handheld GPS |
| trip distance, the bearing, and also information | | | | One of the features that are useful in a handheld |
| about the sunrise and sunset times. If the user | | | | GPS should be that it is waterproof. No matter if |
| inputs their destination, then the distance to the | | | | you are hiking, fishing or boating, if it falls into |
| target can also be tracked. | | | | water and it isn't waterproof, it will be ruined. You |
| The Control Stations | | | | may want to take into consideration whether the |
| At the moment there are eleven control stations | | | | GPS runs on disposable batteries, rechargeable |
| on earth that track the satellites and send the | | | | ones, or ones with an internal battery that can be |
| data onto the master control station. With eleven | | | | charged at home. Many can also be charged with |
| control stations, every satellite can be seen by | | | | a car charger adapter or through a USB cable. |
| two control stations or more. There are plans for | | | | |