We are measuring Vm, RTm, sinkage and trim. For normal conventional merchant ships we will ignore this, this is important for other types of vessels, but not for conventional displacement type merchant ships moving below 0.3 Froude number. What else do we know? We know model displacement, model weighted surface, length on water line of the model, and we will see what else is required- all this is known. We have also measured, we also have to measure temperature of water, because the density and kinematic coefficient- these two items that are very important for our calculation- are temperature dependent, so you have to measure the temperature to get these values.