Drone Light Show 101 | What is RTK and why is it important
What is RTK and why is it important
- The distance from a drone to a satellite is measured by the time it takes for a satellite’s signal travel to the drone’s GPS receiver. With a same clock implemented both inside of the satellite and drone, GPS signal sending and receiving time difference can be calculated. Multiply with the speed, as the signal travel as light speed, we can calculate the distance.
- While GPS receiver measures the distance to four satellites, its three-dimensional position can be determined. This is the basic scenario when a drone locating its own position.
- However, we know that satellites are outside the atmosphere, the interference to satellite signals during passing through the atmosphere, especially the ionosphere, is very large. Beyond that, there are other errors like signal multipath due to reflection, satellite and receiver internal clock errors and noise, etc. All these errors result in the drone location error about two to four meters.
- At this point we introduce a RTK base station nearby the drone, and maintain a fixed position. The RTK base station can process another independent locating method to acquire its precise coordinate, called survey in. Compare this coordinate with GPS location, GPS signal propagation error can be computed. As base station is vicinity of the drone, satellite signal and propagation errors received by basestation is identical to the drone. the drone utilize this correction data as solution to eliminate propagation errors. And thus drone’s position error can be narrowed down to achieve centimeter accuracy.
- This is how RTK works. We turn this scenario into drone light show, by setting a RTK base station on field, run survey in process, then base station will broadcast RTK correction information by radio continuously. And thus every single drone will receive the RTK correction information throughout the drone show process, to maintain its centimeter positioning.
- Survey in process can be trigger in our software Vimdrones GCS. Survey in during time and minimum accuracy are adjustable according to satellite condition, an appropriate setting will give you efficient and ideal locating result. Once survey in succeed,
- The smaller ACC value, the closer base station to the GLOBAL coordinate. Larger ACC value, the easier for survey in succeed. Since drones and base station form a LOCAL RTK correction relationship, generally setting ACC to 5 meters is sufficient for centimeter positioning and for easy survey in.