What is GPS?
The Global Positioning System (GPS) is a space-based radio-navigation system consisting of a constellation of
satellites and a network of ground stations used for monitoring and control. A minimum of 24 GPS satellites orbit the
Earth at an altitude of approximately 11,000 miles providing users with accurate information on position, velocity, and
time anywhere in the world and in all weather conditions. By locking onto these signals using a GPS receiver, one can
determine its precise location.
What is GPS receiver?
A GPS receiver obtains information from the system of 24 GPS satellites rotating the earth – FOR FREE! While
outdoors and depending upon the weather, a GPS receiver will be able to determine your position, at any time of the
day, from any place on the surface of the earth, provided that you have a clear view of the sky.
GPS receiver determines your latitude, longitude, altitude, heading, speed, time, date and other technical information.
The receiver passes this data along to your computer or handheld in the form of a generic protocol called NMEA,
which most Marine and Street navigation software can read. After receiving the information from the GPS receiver, it is
the software’s job to plot you on a map, guide you on road trip, or help you navigate oceans. With a GPS receiver,
good sense, and the appropriate software, you can go just about anywhere without getting lost.
How GPS determines your position?
A GPS receiver simply measures the travel time of the signals transmitted from the satellites, then multiplies them by
the speed of light to determine exactly how far the unit is from every satellite it's sampling. By locking onto the signals
from a minimum of three different satellites, the GPS receiver can calculate a 2D (two-dimensional) positional fix,
consisting of your latitude and longitude. Looking onto a fourth satellite allows the GPS receiver to calculate a 3D
(three-dimensional) fix, calculating your altitude as well as your latitude/longitude position.
How accurate a GPS receiver can provide?
The greater the number of satellites you GPS can “see”, the more accurate it will determine your position. The number
of satellites that your GPS is able to acquire depends on the time of day and your location. Thunderstorms, tall
buildings, and dense overhangs can block the signals from the satellites. Also keep in mind, that due to military
restrictions , GPS receivers for recreational or commercial purposes are only accurate to within approximately 9-30 fee
(3-10 meters).
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