Ground Distance and angle of attack definition on Ground effect analysis

[AGUS SUDARMAWAN]

Dear Rob McDonald, I want to perform wing in ground effect analysis by using VSPAero. I need your advice regarding :

1. Ground distance. What is the distance definition when I put a distance number on the input pad? It is distance the nearest model surface point to ground? or distance from 25%c MAC Wing Point to ground? or other definition?

2. When I will vary the angle of attack, do i have to change through the angle of attack input number? or I have to rotate the model to simulate the angle of attack?

Thanks for your advice and response.

Agus Sudarmawan