For each contour detected, a centroidal map is computed.
This map gives the distance between a point P on the
contour and the object centroid G, plotted verms the angle
formed by the half-line GP and a given direction (e.g. the
horizontal direction). Starting from the centroidal representation,
it is possible to detect the prow of a ship by
using geometry and symmetry properties of the ship’s
shape. These characteristics are generally well preserved
even if the ship location varies. The relationship between
the precision of the prow detection and the aspect angle,
i.e. the angle formed by the radar beam and the ship-prow
orientation (Figure .5), is discussed later.