SOWFA+FAST: Wind1VelX output parameter

Good morning,
I am a user of SOWFA+FAST (fastv8DriverProgram-OpenFOAMcoupling coupled with SOWFA) and I have a question about one of the FAST’s output parameters: Wind1VelX.
In my cases,the flow is managed by OpenFoam (CompInflow = 2 in the file .fst), therefore the file InflowWind.dat is neither initialized nor used.
Between the outputs coming from FAST there are also Wind1VelX, Wind1VelY and Wind1VelZ.
My question is: where these parameters are mesured? maybe, are they measured at a fixed distance from the rotor’s hub and the information is taken from OpenFoam? Can you give me some explanations about them? On manuals and guides I haven’t found anything useful for my problem.
Thank you for your attention,

Kind regards,

Andrea Frigerio