1. An optical angle of arrival measurement system, comprising: a focal plane array (FPA) comprising an M row×N column array of pixels, said rows and said columns being parallel to a row axis and a column axis, respectively; one or more optical elements arranged to converge incoming light from one or more sources onto said FPA, such that light from each of said sources is converged into a respective pair of perpendicular narrow width lines that form respective crosshair patterns on said FPA, each of said lines being oblique with respect to said row and column axes and traversing at least two of said rows or columns along its length, such that the position of said lines on said FPA varies with the angular position of each light source relative to said measurement system, said optical elements arranged such that the center point of each crosshair pattern is at least twice as bright as the perpendicular narrow width lines which form the arms of said crosshair pattern; and a means for interpolating the positions on the FPA of each crosshair pattern, comprising: selecting a center point on said FPA, the location of which is to be determined; defining at least two regions on said FPA around said center point, each of which includes at least a portion of a respective one of the arms of the crosshair pattern associated which said selected center point; for each of said regions, determining the coordinates of the point of peak intensity in each row or each column within said region; and curve-fitting said peak points to define each arm of the crosshair pattern.