# Curved space geometry

If i have a volleyball and draw a circle around the centre, then draw a line between the top of the ball and the centre and measure the two line I find that the ratio circumference of the circle to diameter of the circles is 4, thus implying that in this case pi is 4, however if I drew a circle of a different size I would get a different ratio.

Could anyone tell me if the value of pi changes in curved space, or if it is the equations that need to be updated?