1. A method of tracking speckle displacement between a first complex image and a second complex image, comprising the steps of: (a) calculating at least one coarse displacement estimate for at least one image location from the first complex image comprising a first real portion and a first imaginary portion and the second complex image comprising a second real portion and a second imaginary portion, wherein calculating comprises: (i) reducing the resolution of the first complex image and the second complex image; (ii) correlating at least an image subset of the first reduced resolution complex image with the second reduced resolution complex image; and (iii) for each pixel in each of the first reduced complex image and the second reduced complex image, calculating the location of the maximum value of the correlation function as a coarse resolution displacement estimate by calculating the maximum value of the square of the correlation function; and (b) calculating at least one fine resolution displacement estimate from at least one coarse displacement estimate, the first complex image, and the second complex image.