The VPS system is not a engineering secret. Every chinese drone that is coming out has one. On the IMU, you said the IMU controls the direction and position in the air. I don't believe that's accurate. The rest I agree on.
Can you tell me what is accurate Ansia? My understanding is that the gyroscopic and the magnetometer elements of the IMU controls the direction and position in the air.
"A gyroscope is a device that uses Earth's gravity to help determine orientation. Its design consists of a freely-rotating disk called a rotor, mounted onto a spinning axis in the center of a larger and more stable wheel." Accelerometer vs. Gyroscope: What's the Difference?
I know the GPS system also contributes to this and I have said I mean to look at this.
Can you tell me what you think is accurate with some links?
I only want to be accurate, so I am hoping you will help me.