Improvements in Cloud Photogrammetry Using Airborne, Side-Looking, Time-Lapse Cameras

Abstract

An airborne photographic system, in which the cameras are coupled with an inertial navigation system, was developed and used in a 1978 convective cloud study, Photogrammetric analysis from such a system is enhanced: cloud-feature positions can be determined without external references such as the earth's horizon or cloud base in the photographs, and the data reduction process can be considerably automated. This paper describes the instrumentation, the photogrammetric theory, and the procedures for obtaining cloud measurements from the photographs. An empirical error analysis based on photographs of terrestrial targets is also presented. Cloud top heights determined without any reference height in the photographs are considered to be accurate to within 440 m at a range of 60 km. The largest source of error in determining cloud top height using the 1978 measurements is the uncertainty in determining the aircraft-to-cloud distance rather than inaccuracy in the photographic system. This error can be reduced in future programs by flying as closely in altitude as possible to the cloud features of interest.