For knowing lift to drag ratio (L/D ratio) it suffices to evaluate the angle of elevation. Tan(elevation angle) = L/D ratio. However, this does not give the absolute values of lift (L) or drag (D). For that you measure the pull with a steelyard and wind speed with an anemometer. Now you have the pull vector: so you can determine both lift and drag vectors then respective coefficients if you know the kite area.