We study two related quantities which generalize the concept of upper Banach density of a set to two measurable subsets of the plane. The first of them allows us to generalize a classic result on sufficiently large distances realized in a set of positive upper density, to distances between points of two sets satisfying an appropriate density condition. The second one allows us to show that for all sufficiently large scales $t>0$ and for a smooth, closed, centrally symmetric, planar curve $Γ$ which bounds a convex and compact region in the plane and is of non-vanishing curvature, the family consisting of portions of translates of $tΓ$ has the maximal possible Vapnik--Chervonenkis dimension.