USGS color infrared, 1982 Aero Graphics, 1995 Aerial photographs can be divided into two classes, based on their perspectives. These are vertical and oblique. Vertical-perspective photographs are produced by aiming a camera straight down at the center of the earth. Such images are commonly used in mapping, survey, and reconnaissance applications, and are often made by high-altitude aircraft or satellite. The benefit of this type of photograph is that it can be combined in a sequence of overlapping photos to provide a geographically accurate representation of a large area. The disadvantage is that it contains little three-dimensional information, since all objects are viewed from straight down. Oblique-perspective photographs are produced by aiming a camera at any angle other than perpendicular to the earth's surface. The benefit of such a view, of course, is that it shows objects from their sides. This not only provides a much greater amount of three-dimensional information to the viewer, but is also a more natural view. A major disadvantage to this perspective, in photographic terms, is that only a portion of the photo falls within the range of useful interpretation. As objects approach the horizon, they recede into the distance or are otherwise obscured. The Aero Graphics technique combines the benefits of both the vertical and oblique perspectives into one axonometric image. Namely, it combines a geographically accurate vertical image of an area with a constant-perspective side view of all three-dimensional objects on the surface. Wherever a viewer looks at the image, it appears that he is looking from an oblique perspective, yet the horizon (or the foreground) is never encountered. Such a view is immensely useful in depicting the recognizable three-dimensional aspects of structures, buildings, and landmarks, while retaining the familiar map-like dimensions of the surrounding geographical area. It is applicable to an area of infinite size. The two pictures above offer a side-by-side comparison between a standard high-altitude aerial photo and the Aero Graphics photomosaic, both excerpted from pictures of the entire San Francisco peninsula.   Return to Aero Graphics' Home Page