A computer system running image processing software receives an identification of a desired geographical area to be imaged and collected into an oblique-mosaic image; creates a mathematical model of a virtual camera looking down at an oblique angle, the mathematical model having an oblique-mosaic pixel map of the desired area encompassing multiple source images; assigns surface locations to pixels included in the oblique-mosaic pixel map; creates a ground elevation model of the ground and vertical structures within the oblique-mosaic pixel map using overlapping source images of the desired geographical area, wherein the source oblique images were captured at an oblique angle and compass direction similar to that of the virtual camera; and reprojects, with the mathematical model, source oblique image pixels of the overlapping source images for pixels included in the oblique-mosaic pixel map using the ground elevation model to thereby create an oblique-mosaic image of the desired area.