Get On The Map With A GPS Navigation Receiver
GPS refers to "Global Positioning System". The GPS receiver or GPS navigation receiver functions on the Global navigation satellite system, the satellite transmits the specific microwave signals and then the GPS navigation receiver, which determines the location, speed, direction and time of the satellite, receives these signals. The GPS navigation satellite receivers are used globally to aid navigation. They are the important and useful devices for scientific and commercial purposes and also for making maps and land surveying. Other applications where GPS navigation receivers are used are in the study of seismic waves and to provide the accurate time reference for the synchronization of the telecommunication networks. A GPS navigation receiver is a small chip or a radio receiver that can determine the signals of different satellites at the same time. The GPS navigation receiver is used to calculate its position by calculating the time delay in sending the microwave signals to three or more GPS satellites and then receiving the signals back to it. This technique of calculating the position is called trilateration. Since these receivers do not have precise clocks, the receivers to correct their clock error track one or more additional satellites. Each GPS navigation satellite has three segments: control segment, space segment and user segment. The GPS satellite sends the signals that contain some information like time, week number of the GPS and the health information of the satellite. This information is sent in two parts of the message. The first part is called ephemeris and the second part is called almanac. Ephemeris is valid only for 4 hours and it is updated after every two hours. The course orbit and status information of each satellite is given by almanac. The GPS navigation receiver then receives these signals. Based on the data or information sent by the satellite, the GPS receiver makes a list, which describes the position and direction of the satellite which is further based on the stored or saved position or time of the satellite.
While calculating the position, the accuracy factor is considered and there are many error sources present. When any GPS receiver calculates the position, then the data, which it needs, must contain the current time, the position of the satellite and the measured delay of the received signal. The position accuracy is mainly based on the position of the satellite and signal delay, the time taken in sending and receiving the signal back. Position accuracy can be improved and this can be achieved by using the higher chip rate signals. By doing this position accuracy of about 30 centimeters can be achieved. The main factor that affects the accuracy is the electronic errors in the GPS receiver. These errors degrade the accuracy of the receiver. Some of these errors are: ionospheric effects, ephemeris errors, satellite clock errors, multipath distortion, tropospheric effects, and numerical errors. One available GPS navigation receiver is Ambicom GPS Navigation Receiver CF Card. The civil application of GPS receivers is in code division multiple access cellular phones and emergency calls. GPS navigation receivers are available in various forms like, extended complex flash card GPS mice, and Bluetooth GPS. |
