Why camera synchronization is so important
Usually autopilot triggers the camera and records the coordinate it has at that moment. When the drone is flying at 20 m/s and GPS works at 5 Hz, that means your autopilot will have position readings only each 4 m, which is not suitable for precise georeferencing. In addition, there is always a delay between the trigger and the actual moment the photo is taken.
Reach eliminates the delay
Reach solves the problem of positioning by connecting directly to the camera hot shoe port, which is synced with the shutter. The time and coordinates of each photo are logged with a resolution of less than a microsecond. This method allows GCPs to be used only to check your accuracy.