- 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,