- 1403 - 
ROLE AND APPLICATION OF HIGH ALTITUDE AERIAL PHOTOGRAPHY 
IN THE HUMID TROPICS WITH SPECIAL REFERENCE TO SIERRA LEONE 
J.A. Howard and D.C. Schwaar 
Food and Agriculture Organization of the United Nations 
ABSTRACT 
This paper reviews previous publications on high altitude aerial photography 
and reports on the use of high altitude photography for land resources survey 
in Sierra Leone. High altitude aerial photography (high flight photography) 
was chosen to provide national coverage of Sierra Leone after careful 
consideration of a number of constraints including long periods of cloud 
cover. Environmental Satellite imagery (i.e. NOAA imagery) was used to 
assist in choosing the season for photography. 
Results indicate that high altitude aerial photography has distinctive 
advantages and could be used advantageously in many parts of the world to 
provide remote sensing data quickly and relatively cheaply of extensive 
areas and with a resolution far superior to other sensors operating under 
comparable conditions. 
I. INTRODUCTION 
As outlined in this paper, high altitude aerial photography was chosen to 
provide national coverage of Sierra Leone in the presently executed FAO 
land resources survey project. This was the first occasion that colour infra- 
red (CIR/IRC) HA photography had been used extensively in the humid (i.e. 
moist/wet) tropics; and the sensor combination was chosen after careful 
consideration of a number of constraints, which will be identified later. 
The term "high flight aerial photography " HFAP) may be used as a synonym 
for "high altitude aerial photography". Both terms will be used in this 
context when referring to photography taken by an aircraft operating above 
the normal ceiling of an unpressurized aircraft (i.e. above about 8000 m)- 
end therefore excludes photography from balloons and space rockeis such as 
Skylark. 
Resolution is considered unsuitable as the criterion to be used in identifying 
high altitude aerial photography, since the quality of the camera lens and the 
film-filter combinations are being continually improved. Photographic scale 
is also considered unsuitable as & criterion, since it is so readily varied 
by changing the focal length of the camera lens and by so doing can provide 
photography at the same scale and with an information content similar to 
conventional very small-scale photography taken by an unpressurized aircraft. 
II. THE DEVELOPMENT OF HIGH ALTITUDE PHOTOGRAPHY 
The potential importance of high altitude aerial photography for civilian 
purposes was high-lighted about ten years ago by Bock (1968), using a Lear-Jet 
at 13,500 me Test strips of aerial photographs were obtained in Arizona,