System and method for the calculation of the approach speed during air to air refuelling operations

A method for calculating the difference in speed between a receiver aircraft and a tanker aircraft in an approach operation for conducting a refueling operation using a hose and drogue device, wherein it comprises the following steps:

• a) obtaining a sequence of digital photograms of the approach operation from a place on the tanker aircraft that enables lateral viewing of said scenario knowing the real distance corresponding to a pixel of a photogram;
• b) obtaining the 2D coordinates of the relative trajectory of receiver aircraft shown in said sequence of photograms with respect of tanker aircraft by means of the following sub-steps:
• b1) selecting in the first photogram a pattern area of the receiver aircraft having a small size, in which a portion of receiver aircraft is visible, and obtaining and storing the 2D coordinates of its midpoint, and identifying a reference frame of pattern area having the same midpoint, shape, and a larger size than that of the pattern area of a predetermined scaling factor;
• b2) searching for pattern area of the previous photogram on the next photogram within the reference frame identified in the previous photogram and, once found, using it as the new pattern area, obtaining and storing the 2D coordinates of its midpoint, as well as the instant in time of photogram, and identifying and defining the reference frame of the said new pattern area in the same way as in the previous sub-step;
• b3) repeating sup-step b2) for the rest of the photograms of the sequence;
• c) calculating the difference of the speed between receiver aircraft and tanker aircraft, based on the trajectory defined by the 2D coordinates of each pattern area midpoint stored in step b).