The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. GPS works in any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS.
GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information to earth. GPS receivers take this information and use triangulation to calculate the user's exact location. Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with distance measurements from a few more satellites, the receiver can determine the user's position and display it on the unit's electronic map.
Factors that can degrade the GPS signal and thus affect accuracy include the following:
- Ionosphere and troposphere delays — The satellite signal slows as it passes through the atmosphere. The GPS system uses a built-in model that calculates an average amount of delay to partially correct for this type of error.
- Signal multipath — This occurs when the GPS signal is reflected off objects such as tall buildings or large rock surfaces before it reaches the receiver. This increases the travel time of the signal, thereby causing errors.
- Receiver clock errors — A receiver's built-in clock is not as accurate as the atomic clocks onboard the GPS satellites. Therefore, it may have very slight timing errors.
- Orbital errors — Also known as ephemeris errors, these are inaccuracies of the satellite's reported location.
- Number of satellites visible — The more satellites a GPS receiver can "see," the better the accuracy. Buildings, terrain, electronic interference, or sometimes even dense foliage can block signal reception, causing position errors or possibly no position reading at all. GPS units typically will not work indoors, underwater or underground.
- Satellite geometry/shading — This refers to the relative position of the satellites at any given time. Ideal satellite geometry exists when the satellites are located at wide angles relative to each other. Poor geometry results when the satellites are located in a line or in a tight grouping.
- Intentional degradation of the satellite signal — Selective Availability (SA) is an intentional degradation of the signal once imposed by the U.S. Department of Defense. SA was intended to prevent military adversaries from using the highly accurate GPS signals. The government turned off SA in May 2000, which significantly improved the accuracy of civilian GPS receivers.
REASONS FOR USING THE GPS PAL
- No more spots on windshield
- Safer, better vision with nothing on the windshield
- No more reaching over your steering wheel to program your GPS
- No more letting the sun heat your unit up to 160 degrees when mounted on dash or windshield.
- No more long wires hanging over your dash, GPS pal stores wires by rolling up excess wires and putting in the bottom of GPS-pal.
- Removing from windshield makes it less of a target for thieves to see and steal or vandalize your vehicle.
- No more buying windshield suction cups or new windshield mounts because the sun dries them out.
- No more putting dash mounts that glue on and almost impossible to remove without messing up your dash.
- GPS-Pal is very versatile and can be moved form one vehicle to another by just unplugging from your power source and switching to another vehicle plug in and go.
- Have a great driving experience and enjoy your GPS they
are fun to use and get you where you need to go.
