Ey Cue components can be said to be really sufficient or satis- But it is in the training of observers, in detailed
iB of factory. But the defects of the first two are quantita- study of sea ice characteristics, and in climatic
soin tive, not qualitative; only ice reconnaissance suffers studies that photo-interpretation comes into its own.
ago from the drawback of being dependent on the visual In training ice observers its use is clear; recognition
; judgment of the observer. This is obviously an undesir- of ice types, estimating of size and concentration of
of able situation - however well trained or experienced floes - such things would be hard to teach without the
of the observer may be, his estimate remains subjective extensive use of air photographs. Color photographs are
g to &nd inexact. Considerable thought has been given to particularly valuable in this field, as color plays such
ce in devising a more reliable means of securing ice infor- an Important part in determining the age of ice.
ice- mation, and among the methods investigated is the re-
usually placement of visual observations, pecorded m flight In climatic studies and studies of ice characteristics,
A found on a map, by photography. Dr. Geza Teleki+ has studied which to & large extent go hand in hand, photography can
Oy this question in the Beaufort Sea, and considers that be an invaluable tool. In this field, sampling tech -
photographs scanned electrically could provide a solu- niques are completely satisfactory, and periodic photo-
tion. However, he sidesteps the question of frequency graphy of selected sample areas, in conjunction with
the and extent of coverage, admitting that it is not prac- visual reconnaissance on a wider scale, can yield ex-
tical to cover the whole forecast area by daily or near- cellent results. This technique, in a rather simple
iy ice daily photo-reconnaissance, but failing to suggest any form, was used some years ago in & series of flights
tho 3 workable alternative. This would seem to rule out photo- organized by the Defence Research Board of Cenada, in
of a interpretation completely as a substitute for visual re- conjunction with the RCAF, the Meteorological Service,
but connaissance. The forecaster needs to know the whole and McGill University, to determine the extent of winter
is ice picture at the time of making the forecast. To ice cover in Hudson Bay. A series of monthly flights
fore photograph the whole picture would be impractical for from November to March was made over the same track by
o many reasons; unreliability of weather conditions, ex- an aircraft equipped with a trimetrogon camera. Single
t 49 pense, and also the time element - time consumed in trimetrogon fans were exposed at intervals of about 10
esent. taking and processing the enormous number of photo- minutes. This was sufficient for the immediate purpose
sen graphs involved, and also in scanning them, even by of the operation, but & more refined application of the
"A electronic means. To use some kind of sampling tech- same technique, giving &t least some stereo coverage,
vos nique, photographing selected strips or sections, would would provide material for more detailed studies.
TE defeat its own object and be no better than visual re-
ne connaissance - probably worse. One of the important points about photography in
nt climatic ice studies is the permanence of thé record
oti This does not mean, however, that photo-interpreta- made of a highly impermanent medium. A clear and ac-
eue tion has no place in the study of ice conditions. Quite curr&te record is obtained of actual conditions in a
= the contrary. Forecasting is not the only aspect of given place on & given dete, which will be invaluable
Sur | sea ice study; and even in reconnaissance for forecast- for comparative climatic analysis after a lapse of
LO | ing purposes, photography can be a useful auxiliary aid. years. It is also always available for checking new
à | Photographs can be taken of special features either as theories and techniques. Workers in fields concerned
hole an aid to correct plotting or for later study and more with land surfaces can at any time go back and check
detailed interpretation. As far as I know this is not the validity of new ideas on the ground. But the
098" at present a practice in the North American Arctic, but Student of sea ice, owing to its ephemeral nature, can
m 1t 1s, I believe, done in the USSR. do this only as far as the current season is concerned.
dps. It is only with the aid of & regular series of photo-
graphs that new theories can be tested climatically,
"e over a period of years.
gical To sum up, it is my opinion that photo-interpretation
aken, hae little direct usefulness in forecast reconnaissance,
re" but that it has many other applications in the study of
dian References: sea ice: as an auxiliary aid in forecasting, as a train-
n une ing aid for ice observers, and as a basic tool in climatic
nr 8 lreleki, Geza. "The Utilization of Aerial Photographs and other studies. At the present time only the second
or. e in Sea Ice Forecasts." In Arctic Sea Ice, National of these, the use of photography as a training aid, is
nd un- Academy of Sciences, National Research Council, fully exploited in North America. The other fields, and
ick Pub. 598. Dec. 1958. Research under AINA Contract especially the last, should be further investigated.
otis | Nonr 1138(01) with Office of Neval Research.
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