With the latest TOD4 upgrade of the Cathcart Circle Line, you can now take great pictures of the UFO crash in photo mode. Definitely one of the most original Mastery Rewards! But why cows instead of little grey aliens remain standing at the wreck is a mystery?
The movies were wrong. Not only did the UFO crash in Scotland instead of North America, cows are actually a highly advanced species spying on us humans and feeding back that data to their home planets! In a few years, they will have enough data to completely take over the Earth!
I think it's between Patterton and Whitcraigs. More precisely, north-west of Whitecraigs train station. If you position yourself there on the map, you can use the free camera to get to the UFO.