I am calculating the installation angles for a taxi light and a landing light. For that I need to know how far ahead of the vehicle I need to focus these lights. I assume the focal point for the taxi light should be closer than that of the landing light, but have no idea what should be the numerical values of these two distances. I think the landing light focus distance should depend on the approach speed, for that my airplane has a 60 knot approach speed. Please help.