Trebuchets aren't really a tool for defence. They have tremendous range and aren't exactly speedy to load, aim, and launch.
Unless you meant defence in the same way that a country's military operations are known as "defence forces" regardless of intent, in which case carry on.
Thanks for this, I'm going to try this out on my way home. My main use for Gmaps is to determine the quickest way to and from work during peak hour, so keen to see how Magic Earth's traffic data compares.