the curvature at γ ( s ) is always given by − 3 π lim$_{r}$$_{→}$$_{0}$ ∂ ∂r g ( s,r ) πr 2 . The available data (the values g ( s, r ) for all s ∈ [0 , L ) and all r ∈ (0 , ϵ )) are sufficient to compute the relevant derivative and limit so we can use this process to determine the curvature of every point on the C 2 curve ∂ Ω. 117