optical illusion from fast motion

Came across an interesting issue, that baffled me for about 6 hours. Beware repetitive tiles when moving about 50-60 mph or more. It will make your eyes think your vehicle is moving backwards or sideways when it isn't. I created a wonderful mountain scene to fly in and put just one texture on it while setting up the rest. During flight tests my plane appeared to go backwards if I didn't takeoff before 50 mph. I finally noticed that an in scene object had correct relative motion despite my eyes telling me I was moving sideways and realized I had been chasing an optical illusion. Issue went away once I added CTS to break up the patterns on the terrain.