Formation of reference images and decision function in radiometric correlation­extremal navigation systems

Methods for formation of reference images (RI) and unimodal decision function (DF) have been developed to ensure efficient functioning of radiometric correlation­extreme navigation systems (CENS) of flying machines (FM). The methods were developed for the conditions of CENS position finding on the surfaces of sighting (SS) with a highly developed infrastructure at insignificant altitudes of flight of the flying machine which leads to formation of current images (CI) with a non­stationary structure. Non­stationarity of CI arises when geometric conditions of sighting the three­dimensional objects change. The method of RI formation is based on the use of a set of three­dimensional stationary objects with the highest radio­brightness temperature, their contouring and determination of mean radiobrightness temperature. A method for forming a unimodal DF of radiometric CENS which takes into account three­dimensional form of SS objects, spatial position and orientation of the FM was developed. The method is based on CI pre­processing which consists in its layering with respect to the mean radiobrightness temperature of background and determination of a set of objects with the highest radiobrightness temperature. The set of objects defined by their contouring is used as a geometric invariant with an informative attribute in the form of average radiobrightness temperature. It was established by simulating the process of formation of DF that pronounced unimodal DFs are formed at signal­to­noise ratio (q=5...10) at the output of the radiometric channel. At the same time, the possibility of correct localization of the binding object in TI is close to unity and reduction of influence of perspective and scale distortions of images on accuracy of CENS location is ensured. The simulation results have confirmed effectiveness of the proposed methods of formation of RI and DF for location of radiometric CENS on the sighting surfaces with complex three­dimensional objects leading to formation of a non­stationary CI.