Tech Chat – How does GNSS work?

No matter as a surveyor or other ordinary people, everyday we are using GNSS (Global Navigation Satellite System) in our daily work or life, such as GPS and BDS. Have you ever wondered how GNSS works?

The global navigation satellite system consists of three parts: ground control part, space satellite constellation and ground user equipment. And the ground user part is closely related to our daily life.

Ground Control Part  

It consists of main control station, monitoring station, ground antenna and communication auxiliary system (data transmission).  

The main control station is responsible for collecting tracking data of each monitoring station, calculating satellite orbit and clock parameters, and sending the results to the satellite through the ground antenna. At the same time, the main control station is also responsible for managing and coordinating the work of the whole ground control system.  

Each global system has a number of monitoring stations equipped with sophisticated atomic time standards and many receivers that can continuously measure all visible satellite pseudoranges. After correcting the measured pseud distances using ionospheric and meteorological parameters, data with a certain time interval is generated and sent to the master station.  

Each global system has many monitoring stations equipped with precise atomic time standards and many receivers that continuously measure pseudoranges from all visible satellites. After correcting the measured pseudoranges using ionospheric and meteorological parameters, data with time intervals are generated and sent to the master station.

A special ground antenna is arranged on the same site of the monitoring station. The ground antenna is equipped with equipment to transmit commands and data to the satellite and receive telemetry and ranging data from the satellite. All operations of the ground antenna are carried out under the control of the master station. 

Space Satellite Constellation  

The space satellites of the global positioning satellite system generally operate in the space about 20000 km above the ground. Twenty-four to thirty satellites form a constellation, which is distributed in three or six orbital planes according to the structure design, with the same angle between adjacent orbits.  To ensure the continuous operation of the system, a backup satellite is usually deployed in each orbit, which can be replaced immediately if any satellite fails.  

Ground User Equipment  

The user equipment part is the position and navigation signal receiver.  Its main function is to be able to capture satellites and track their movements.  When the receiver captures the tracking satellite signal, it can measure the pseudo distance from the receiving antenna to the satellite and the change rate of the distance, and demodulate the satellite orbit parameters and other data.  According to these data, the microprocessor in the receiver can carry out positioning calculation according to the positioning solution method, and calculate the longitude and latitude, altitude, speed, time and other information of the geographical location of the user.

The theory may seem a little complicated, but when it comes to practical applications, you will find it very familiar. There are various types of satellite signal receivers, including airborne navigation receivers used in aerospace, aviation and navigation, surveying receivers used in heading and positioning, and vehicle-mounted and hand-held receivers used by the general public.  

At present, the most common satellite navigation systems in the world include: GPS in the United States, GLONASS of Russia, BDS of China and Galileo of the European Union, as well as QZSS of Japan and IRNSS of India. All these systems are supported by our GNSS devices, like Y1 GNSS receivers, T8 Pro Tablets.

It is precisely because of the cooperation of multiple parts that centimeter-level positioning accuracy can be achieved to meet the needs of industries such as surveying and mapping, monitoring, machine control, and precision agriculture. GNSS is gradually entering our lives and subtly changing our world. This is also what we at SingularXYZ are trying to do - popularize precise intelligence in all aspects of people's lives, and contributing to the construction of a digital, intelligent and efficient open society.

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