Drone's GPS positioning system is a core component of its flight stability and precise control. GPS (Global Positioning System) determines the drone's location, speed, heading, altitude and other information by receiving satellite signals. Here is how the GPS positioning system works in drones:

 
1. The basic principle of GPS positioning
The working principle of the GPS positioning system is based on triangulation. Global GPS satellites regularly send signals containing time and location information in space. The GPS receiver on the drone receives signals from at least 4 satellites and calculates the specific location of the drone through the following steps:
Distance calculation: The drone receives the signal from each satellite and calculates the distance to each satellite based on the time the signal travels. The farther the distance, the longer the signal travels.
Positioning calculation: The three-dimensional position (longitude, latitude and altitude) of the drone is calculated using triangulation using signals from at least 4 satellites. Three satellites provide horizontal position (latitude and longitude), and the fourth satellite is used to calculate altitude.
Time synchronization: Since there is a time delay in the propagation of satellite signals, the GPS receiver also needs to be time synchronized to ensure the accuracy of the calculation.

 
2. GPS system composition
The GPS system of drones consists of the following parts:
GPS satellites: There are about 30 GPS satellites in orbit around the world, and at least 24 are actively working, which continuously send signals to the ground.
GPS receiver: The GPS receiver on the drone is responsible for receiving signals from satellites and determining the position of the drone through calculations. Modern drones are usually equipped with high-precision GPS receivers that can provide stable positioning in harsh environments.
Flight control system (FCU): The flight control system controls the flight trajectory, speed and altitude of the drone based on the position data provided by GPS to ensure stable flight.

 
3. Functions of drone GPS positioning
Position holding: Through the GPS positioning system, the drone can maintain a fixed flight position and even hover stably without control input. The GPS positioning system helps the drone continuously adjust its position during flight to prevent deviations caused by wind or other factors.
Automatic return to home (RTH): If the drone loses the remote control signal during flight, or the pilot manually activates the return function, the GPS positioning system can help the drone automatically return to the take-off point. The drone will use satellite signals to determine the location of the take-off point and return via the shortest path.
Flight path planning: Some high-end drones support waypoints. Pilots can preset multiple waypoints on the map, and the drone will fly along the predetermined route according to the GPS positioning system.
Accurate positioning: The GPS system can provide accurate location information and support the positioning of drones in complex environments, especially in open areas with stable GPS signals, and can achieve centimeter or meter accuracy.

 
4. GPS accuracy
The accuracy of the GPS positioning system is usually affected by the following factors:
Number of satellites: The more satellites received, the higher the positioning accuracy. Generally speaking, at least 4 satellite signals are received, and the positioning accuracy can reach 1-3 meters. High-end drones can usually receive more satellite signals and have higher accuracy.
Environmental factors: Obstacles such as buildings, mountains, and trees may interfere with GPS signals, resulting in reduced positioning accuracy. Multipath effect may occur in places with high-rise buildings or dense forests in cities, that is, signal reflection causes errors.
Atmospheric interference: The atmosphere in the ionosphere and troposphere will cause a certain delay to the GPS signal, affecting the accuracy.
To improve the accuracy of GPS positioning, some drones use differential GPS (DGPS) or enhanced GPS (such as RTK technology) to further improve positioning accuracy. RTK (real-time dynamic positioning) technology can improve positioning accuracy to centimeter level through differential information provided by base stations.

 
5. Auxiliary systems and redundant systems
In order to improve positioning accuracy and flight stability, drones may integrate some auxiliary systems:
Visual positioning system (VPS): Through cameras or laser sensors, visual positioning systems can provide auxiliary positioning when GPS signals are weak or absent, especially indoors or in complex environments. VPS can assist positioning through image recognition of ground features.
Inertial measurement unit (IMU): IMU integrates accelerometers, gyroscopes and magnetometers, which can monitor the attitude changes of drones in real time and compensate for GPS positioning errors. IMU data can help maintain flight stability when GPS signals are weak.

 
6. GNSS (Global Navigation Satellite System)
In addition to the traditional GPS positioning system, some high-end drones support multi-frequency GNSS receivers, which can receive satellite signals from different countries or regions (such as GPS in the United States, GLONASS in Russia, Galileo in Europe, and BeiDou in China). Using signals from multiple satellite systems can improve the accuracy and stability of positioning, especially in cities or other complex environments.

 
7. Limitations of GPS positioning
Although GPS positioning is a very important technology in drone flight, it also has some limitations:
Signal interference: GPS signals may be unstable or unreceivable in basements, tunnels, or environments with strong electromagnetic interference.
Multipath effect: Due to the reflection and refraction of satellite signals, the received signals may deviate, affecting the positioning accuracy.
High-precision requirements: Some high-precision applications (such as mapping, agriculture, etc.) may require higher-precision positioning systems such as RTK or PPK, which require additional hardware support.

 
Summary
The GPS positioning system of drones receives satellite signals and uses triangulation to calculate its position, speed, heading, and altitude, thereby achieving functions such as position keeping, automatic return, and flight path planning. The accuracy of GPS positioning is affected by factors such as the environment, the number of satellites, and atmospheric interference. Modern drones also integrate auxiliary systems (such as visual positioning systems and inertial measurement units) to enhance positioning stability and accuracy. In flight, combining multiple technologies and redundant systems can greatly improve the safety and reliability of drone flights.