Also called "drones," these planes allow experienced controllers to fly a camera over an area of interest. It is fairly low-cost (the cost of building the plane and acquiring the camera/film) and does not require as much planning as if you had hired an aerial survey firm. Unless you have a method to determine the drone's altitude, it would be very difficult to attain a specific photographic scale. Many of the calculations and planning required for airplanes is necessary, but this method could be useful for frequent monitoring of the landscape.

This paper lists more specific details for building and using a drone:

Quilter, M.C. and V.J. Anderson. 2000. Low Altitude/Large Scale Aerial Photographs: A Tool for Range and Resource Managers. Rangelands 22 (2): 13-17.