1. A non-transitory processor-readable medium storing code representing instructions to cause a processor to: smooth a current image of a scene to produce a smoothed image; subtract pixel values of a background image of the scene from corresponding pixel values of the smoothed image to produce an altitude difference image; weight pixel values of the altitude difference image to produce a weighted difference image; convolve the weighted difference image to produce a convoluted difference image; apply a threshold to each pixel of the convoluted difference image to produce a thresholded difference image, pixels having a value less than the threshold being removed from the thresholded difference image and classified as background pixels; and determine foreground pixels based on the thresholded difference image.