1. A programmed computer system for removing artifacts from aerial images of a region of interest, including: a memory for storing program instructions that are executable by a processor; a processor configured to execute the stored program instructions in order to: receive two or more input aerial images of the region of interest that are obtained at different times; create a three-channel false color image by applying pixel data for a selected band of a first input aerial image to a red color channel of an RGB monitor, applying pixel data for the selected band of a second input aerial image to a green color channel of the RGB monitor and applying pixel data for the selected band of a third input aerial image to a blue color channel of the RGB monitor; identify pixels representing clear areas, clouds and shadows in the two or more input aerial images based on the color of the pixels in the false color image, wherein: pixels representing clear areas in the first, second or third input aerial images are identified by gray pixels in the false color image, pixels representing clouds in the first input aerial image are identified as pixels having a bright red color; pixels representing clouds in the second input aerial image are identified as pixels having a bright green color; pixel representing clouds in the third input aerial image are identified as pixels having a bright blue color; pixels representing overlapping clouds in the first and second input aerial images are identified as pixels having a bright yellow color; pixels representing overlapping clouds in the first and third input aerial images are identified as pixels having a bright magenta color; pixels representing overlapping clouds in the second and third input aerial images are identified as pixels having a bright cyan color; and wherein pixels representing shadows in the first input aerial image are identified as pixels having a dark cyan color and that are nearby pixels having a bright red color; pixels representing shadows in the second input aerial image are identified as pixels having a dark magenta color and that are nearby pixels having a bright green color; pixels representing shadows in the third input aerial image are identified as pixels having a dark yellow color and that are nearby pixels having a bright blue color; pixels representing overlapping shadows the first and second input aerial images are identified as pixels having a dark blue color and that are nearby pixels having a bright yellow color; pixels representing overlapping shadows the first and third input aerial images are identified as pixels having a dark green color and that are nearby pixels having a bright magenta color; pixels representing overlapping shadows the second and third input aerial images are identified as pixels having a dark red color and that are nearby pixels having a bright cyan color; and create an output image of the region of interest by selecting one of the first, second or third input aerial images and replacing pixels that represent cloud or shadow regions in the selected aerial image with pixels representing a clear area from the non-selected first, second or third input aerial images.