A displacement vector is a vector whose length is the shortest distance from the initial to the final position of an object:
s= xf-xi = Δx
Hough-R(r)-Table:
1: Compute r (instead of s but basically the same):
r= c(center of object) – p(i)(point number i)
2:measure the gradient angle θ at the boundary p(i).
3: Store r in a table with it’s θ (multiple r’s can have the same angle θ)
Recognition
measure shapes edges(gradients) again and get their θ, go back to the R table and again check which r’s have the most votes for the same point.