How Accurate Are Waypoint Missions?
GPS Accuracy
Waypoint missions are created by specifying the GPS location of two or more waypoints. Although a GPS location can be specified with great numerical precision, the drone's ability to fly to that location is not equally precise.
Describing GPS accuracy with a single number can be difficult because there are many types of GPS systems, and accuracy can be affected by numerous factors, including satellite geometry, signal obstructions, atmospheric conditions, and the capabilities of the GPS receiver. This is likely why such a wide range of GPS accuracy values can be found online.
Smartphones commonly use assisted GPS (A-GPS), which supplements GPS satellite signals with information from cellular networks and other positioning systems. This can provide better positioning performance than a basic standalone consumer GPS receiver, particularly when satellite reception is limited.
DJI drones, like many consumer devices, use consumer-grade satellite positioning systems. General estimates for consumer GPS accuracy are sometimes quoted as approximately ±3 to 8 meters (10-26 feet). However, these broad figures should not be assumed to represent the actual waypoint accuracy of DJI drones.
DJI's published specifications for horizontal positioning accuracy are considerably better on many of its drones. Older models such as the Mavic 2 and Air 2S are specified at approximately ±1.5 m, while newer models such as the Mini 3, Mini 4, and Mavic 3 are specified at approximately ±0.5 m under the stated positioning conditions.
My experience from flying hundreds of waypoint missions is consistent with DJI's published specifications. When I repeat waypoint missions, the drone generally follows the intended flight path quite closely. I have never observed a waypoint mission to be anywhere near 8 meters (26 feet) away from the intended course.
It is important to remember that positioning accuracy and waypoint repeatability are not necessarily the same thing. The drone's reported GPS position can vary somewhat from flight to flight, but this does not mean that waypoint missions will routinely be displaced by the full amount sometimes quoted for consumer GPS accuracy.
Web sites with good explanations of GPS