GPS Sensor Function | GPS Sensor Working
This page describes GPS Sensor basics including GPS sensor function. It mentions GPS sensor working along with GPS system diagram.
What is GPS Sensor?:
As we know GPS stands for Global Positioning System. The system contains satellites and ground based control installations.
GPS sensor consists of surface mount chip which processes signals from GPS satellites using a small rectangular antenna, often
mounted on the top of the GPS chip.
• GPS module is usually small board on which GPS sensor is mounted with additional components.
• GPS receiver is a device which includes data display and other components such as memory for
data storage in addition to GPS module.
The figure-1 depicts breakout board along with GPS sensor offered by Adafruit industries. GPS system consists of three segments viz. space segment, control segment, user segment. Space segment contains about 31 satellites as of August 2018 which are located in the orbit about 12,500 miles above earth. Hence each of these satellites circle two times in 24 hours. Control segment contains command, control and monitoring stations. USer segment consists of receiving devices (e.g. both government and private).
GPS Sensor Function | GPS Sensor Working
Let us understand GPS Sensor working operation.
➤As shown in figure-2, about four satellites are needed to determine a position on the earth in 3 dimensional space.
Each of these satellites carry multiple atomic clocks which maintain precise time and pseudo random number generator in the form of
linear feedback shift register.
➤GPS receiver can distinguish signals from atleast four satellites by comparing their received pseudo random bit sequences and
can calculate receiver's distance to each of these satellites by comparing arrival times of satellite signals.
➤Distance = transit time (sec) x speed of light (meter/sec)
➤GPS satellites transmit on several frequencies simultaneously.
One such frequency known as L1 (1575.42 MHz) is used for civilian applications
where as the other frequency L2 (1227.6 MHz) is used for military applications.
Refer GPS and GNSS frequency bands >> for more information on
gps and gnss frequencies.
➤GPS module housing GPS sensor requires DC power supply. It starts outputting data as soon as
it identifies the satellites within its range. The data follows plain ASCII protocol known as
NMEA protocol. The transmission rate is either 4800 bps or 9600 bps and uses {8 bits, no parity, 1 stop bit} for decoding.
The data blocks are known as sentences which are of about 80 characters in length.
Refer GPS Sentences >> for more information.
These gps sentences contain latitude, longitude, altitude and data recording time.
These sentences are decoded by connecting microcontroller with GPS module and writing small program.
Refer application note on interfacing of GPS sensor >> with Arduino Uno board with pin to pin block diagram and source code.
GPS RELATED LINKS
What is GPS system? GPS vs AGPS GPS Frame Structure GPS vs GPRS GPS Basics Tutorial GPS Antenna GPS Receiver Module GPS Satellite GPS Tracking System