I was at Walmart and found some black ripstop with some sort of white backing on it. There was about 6 1/2 yards so I bought the lot and did it up. I figure it can be a black cat tarp, or a white cat tarp
I took the bolt width and sewed a flat feld ridge seam. I wasn't sure what to do for the size, so I just measured back a foot and laid out a cat cut type design. The vertical edge curve was 3" offset at the center, the horizontal was 6" at the center of the arc. I bought 7/8" grosgrain ribbon and ironed it folded in half for the other edges after adding reinforcing material in the corners and the ends of the ridge line. Then I just sewed 1" flat webbing for tie straps.
Tarp is approx 10'x10' less the cuts.