Rare sighting of ufo formation shadow on the ground.

I was 14 years old at the time, and was playing in a vacant lot across from my parents house. I was picking up rocks to hit with an old baseball bat, when I suddenly notice a shadow move right between my legs, heading north. It was the shadow of 6 perfect, unattached circles, moving at about walking pace. From my perspective, each circle on the ground was about the size of an over-sized dinner plate. This was a perfectly sunny and cloudless day, but when I looked up toward the sky to see the cause of the shadow, there was nothing. It was quite amazing to me, I remember, that I couldn't see what was causing the shadow, despite it's large dimensions. Any other craft casting a shadow that large would have been easily spotted in the sky. I followed the shadow for about 20 yards until the yard ran out and thich hedges obstructed me. My first immediate reaction was to run inside to tell my parents (since my father had a sighting in 1962, of a green cigar in the night sky over Treasure Island, FL), so I knew that he would ubderstand. My first impression was that I thought that these craft had to be cloaked in some way, maybe by turning the bottoms of the craft to match the clear blue sky.
Date of incident is approximate.  PD