METHOD OF ACCURATELY LOCATING THE FRACTIONAL POSITION OF A TEMPLATE MATCH POINT

A method of accurately locating a sub-pixel maximum on a two-dimensional grid having an x axis and a y axis is provided. The method, which is especially suitable for locating a sub-pixel maximum, which falls intermediate grid point locations, begins by identifying a grid point having a maximum grid point value. Then, a quadrangle containing the sub-pixel maximum is determined by locating neighboring grid points along the x and y axes, which have the next greatest grid point values. Next, four one-dimensional, fractional maxima are computed along each side of a quadrangle. Next, two lines connecting one-dimensional maxima along the opposite sides of the quadrangle are computed. Finally, a location for the sub-pixel maximum is calculated where the two computed lines intersect.