us-X, Double-X
use of high
aphy using
for assessing
Carneggie
ar orbiting
ERTS-1) and to
elius et al, 1973;
wider use of
the successful
here been
rammetric
isappointing
e surveys.
ographs and
969; Draeger
nson, 1969),
t al, 1913).
' about 18,450 m.
| in general;
ilter
| imagery in
ration,
id HFAP imagery
road + S
‚er a om
icluded ?deciduous
ert as grazin
tural mne
pphs, due to
yd identification
;,e photography
of HFAP for
for example,
3 for 'wheat!
j were undesirably
3 and difficulty
F-alfa,
tinger (1972) that
greater than that
ment was not
ssary for increased
= 1465 -
accuracy of crop identification’. This suggests there is no major information
threshold between HFAP at about 1:120,000 and outer space photography at
1:500,000 and the smaller scale Apollo satellite photography(for this
particular type of study). However, in the several state surveys of maize blight
in the USA (1971/72), it was observed, for example, that maize could be identified
on the IR colour photographs particularly by the banding effect of the individual
rows spaced at about O.Tm.
Reference to literature also indicates that there was little attempt in this
period to refine HFAP photo-interpretation for forest studies, although HFAP
had been proposed for multi-stage sampling in forest inventory (Langley, 1972).
Studies of forested areas in Nevada indicated that some species identification
is possible (e.g. pinon pine/ juniper), and that forest stand density classes can
be delineated.
In California (Lauer and Benson, 1973), it was concluded, using black-and-white
panchromatic photographs at 1:15,840 and IR colour photographs at 1:120,000 that
the latter enabled forest type boundaries to be properly mapped, that forest
type identification with the two film-filter combinations had a high correlation
and cost was greatly reduced with the HFAP, It was judged that the cost of aerial
photography would be reduced up to six times and photo-interpretation by half or
more as compared with other conventional photography. However, Hudson et al (1976)
working in Michigan with colour infrared photographs at scales of 1:60,000 and
1:120,000 concluded that only four tree species groups were distinguishable at
these scales as compared with six groups using CIR at 1:36,000.
Further, thematic mapping/thematic surveys in a number of tropical countries
(e.g. Kenya, Ivory Coast, Papua-New Guinea, NW Australia and Sierra Leone) have
indicated that very small-scale photography can be used to successfully map land
units (Howard 1971; Bleeker and Birchall, 1977; Birchall, 1978; Schwaar, 1978 a),
current land-use (Kater and Gordon, 1978; Gordon, 1978; Schwaar, 1978 a} and to
stratify the forests into timber types for ground assessment (Howard, 1976). In
Australia, black-and-white panchromatic photography at a nominal scale of about
1:84,000 {socal length 88 m) have been widely used for many years for photogrammetric
survey including the production of planimetric maps at 1:100,000.
IV. PHOTOGRAMMETRIC CONSIDERATIONS
Although RB-57 and U-2 photography was taken in the USA for civilian purposes
over 10 years ago, a commercial aircraft with a pressurized cabin for this type
of work was not available until the introduction of the Lear-Jet (US) in 1968.
This had a ceiling of about 13,400 meters, a velocity of about 800 km/h and a
range of about 3,000 km. More recently, the Twin jet Mystére 20, also known as
the Fan Jet Falcon (French), has been adapted to commercial HFAP with an absolute
ceiling of 13,700 m, a velocity of 800 kn/h and a range of about 4,250 km; and
the new Lear Jet 24 D has a ceiling of about 15,000 me At a photographic scale
of 1:120, and with a format of 23 cm, theoretically between about 5000 and
13,000 km” of ground area can be photographed per flying hour.