1. An apparatus, comprising: one or more computer readable medium storing image processing software that when executed perform the functions of: analyzing first and second groups of pixels in overlapping geo-referenced source images captured from different vantage points with respect to a geographic area, the first group of pixels of the source images showing the earth and the second group of pixels showing a three-dimensional object on the earth located at a first geographic location, wherein the analyzing is conducted by scanning the first and second groups of pixels with a kernel and generating values correlated to particular geographic locations within the geographic area, some of the values having a first score indicating that the second group of pixels represent the three-dimensional object; and creating a ground confidence map having the values and data indicative of the particular geographic locations represented by the values at least one of the values being the first score and correlated to data indicative of the first geographic location; and a computer system executing the image processing software.