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Analysis Procedure
The analysis of the photographs (or transparencies) con-
sisted of an optical analysis as described above and of a photo-
chamical equidensity analysis. The last was performed using
Agfacontour Professional film, which showed tc be an easy medium
cost method for operetionel interpretation. The equidensity
analysis (also reforred to as density slicing in other papers)
causes a loss of information, the determination of uhich is
deduced mathematically. It results that it is pessible to mini-
mize this information loss by the choice of suitable width and
position of the equidensities.
The equidensity analysis requires a prior densitometric
analysis of the photographs from which the density levels to
be used are mathematically determined. Theresulting contours
after the photochemical process shoued to be useful uhen study-
ing the directional spectrum ; though the limit for color analy
sis uas found to be of eight diffarent density levels. A com-
plete description of the Agfacontour method may be found in (21)
Data Collection
The photographs used in this study were taken by Hasselblad
Camsras on board of a CASA 212 aircraft operating either at 3000
or at 400 meters altitude during the oceanographic missions
NAUCA 77 and DELTA 77, In both the use of aerial imagery was
intended as support to other experiments. Thus that the selec-
tion of transparencies has been limited by the quality and suit-
ability of the existing imagery which in many cases presented
the disadvantage of showing in part a strong sun-glint. This,
es mentioned above, may overemphasize a determined slope direc-
tion, but this error can be compensated if enough. data of the
area are provided by other sources.
The CASA 212 fleu at a speed of 150 knots under cicar sky
conditions, being the scale of the photographs 1: 120,000 and
1:16,0C0 for each altitude of flight. The starting and ending
times of each series of photographs is indicated and the rate is
one each 26 seconds; this rate is variable to allou overlapping
for stereo analysis.
The selection of the transparencies was made ttending to:
i) influence of sun-glint, ii) uniformity pattern of the scene,
iii) contrast, iv) interaction with coastal and/or islands
accidents and v) interest of the area. In total 25 photographs
were selected from which only seven resulted acceptable when
densitometric analysis was performed. In this paper we give the
results of three analysis as an example of the suitability of
the method,