sive photographs would therefore have to be taken, and
yet many of them would be unnecessary. Finally, the
expense Would be difficult to justify because the photo-
graphs themselves would have only very temporary valid-
ity. Within their system based on visual observation,
however, the Russians do use photography as an aid:
the observer may photograph particular features which
he wishes to remember, such as the alignment of an ice
edge. It is true that Scandinavian Airlines System on
their trans-polar flights rely entirely on photography
for ice information; but their problem is not comparable
to the Russian one, since they are concerned only with
a very small area from which only very generalised in-
formation is required. In North America, where the
problem is similar to the Russian, viaual observation
rather than photography is used.
But if there is now no major use of photography in
collecting synoptic information, there are uses for it
in related fields. It is essential as an aid in train-
ing observers, where it is used for the definition of
terms and classification of ice types, and for building
up sets of instructional pictures to illustrate, for
instance, the exaggeration of concentration to a ground-
level observer by means of vertical and low oblique
shots of the same areas of ice. Such points as these
are mentioned in the standard Russian work on the sub-
Ject.
1. K. K. Deryugin and D. B. Karelin. Ledovyye
nablyudeniya na moryakh (Ice Observations at sea).
Leningrad, Gidrometeorologicheskoye Izdatel^stvo
(Hydrologicel and Meteorological Pubiishing House),
1954, p.161-63. A paper by V.I. Avgevich in Proble
Severa (Problems of the North) No. 3, 1959, p. 150-08,
mentions a number of further uses for photogrammetry in
connection with sea ice. This is important information,
and would have been included in the text, had it arrived
in time.
ICE NAVIGATION AND THE ROLE OF PHOTO INTERPRETATION
IN THE CANADIAN ARCTIC ARCHIPELAGO
by Moira Dunbar
Directorate of Physical Research, Defense Research
Board, Department of National Defense, Canada
ABSTRACT
The development of sea routes in the Canadian Arctic
lagged behind that of the Russian Northern Sea Route,
not because it was more difficult or because Canadians
lacked enterprise, but because there was no demand for
such routes. Now the establishment in the Canadian
Arctic of permanent installations that need annual re-
supply has changed the picture, and an increasing num-
ber of ships enter Arctic waters every summer, penetrat-
ing many of the channels of the Archipelago, and en-
countering both one-year or winter ice and older or
polar ice.
To assist these ships, an ice reporting and forecast-
ing system was necessary and has been developed, the
pioneer work being done by the U.S.N. Hydrographic
Office, starting in 1952 in Baffin Bay and later extend-
ing from Greenland to the Bering Sea. After 1957 the
Canadian Meteorological Service took over the Canadian
sector.
Forecasts are based on weather, oceanographic and
ice data. For ice data we are at present dependent on
visual observations, which are bound to be subjective
and inexact. Photography is not considered a satis-
factory substitute, because the complete and frequent
coverage necessary would be impractical, and even if
the photographs were scanned electronically, too time-
consuming; sampling techniques would not be suitable.
Photography can however be extremely valuable in other
ways - as an auxiliary aid in reconnaissance (photo -
graphy of special features to aid in plotting or inter-
ur " :
" Archives ^ 6
27
‘satellites.
Undoubtedly there are possibilities for further use
of photogrammetry. One of the major unsolved problems
is the determination of ice thickness from the air.
There have been some quite promising experiments in-
volving measurement of the aircoupled flexural wave re-
sulting from an explosion on the ice surface, but they
have not been developed, and in any case a photographic
Solution would be cheaper. Accurate measurement of
Small tone gradations in the colouring of young ice
might lead to & solution for the thinner ice types, but
over a certain thickness a quite different method would
be required.
Another interesting possibility is photography, pre-
Sumably employing television, from artificial earth
This could give an idea of distribution in
the most general terms, and even though lacking in de-
tail it would be very useful indeed. It may well be
that experiments are being made in the U.S.S.R. with
Such aims as this in view.
A paper by S.V. Loshchilov in Problemy Arktiki i
Antarktiki (Problems of the Arctic and Antarctic), No. 1,
1959, p. 01-86, outlines & method under investigation
in the U.S.8.R. for determining thickness from vertical
Stereo pairs. The average height of the ice surface
above sea level is read off, and by taking estimated
values for snow thickness, snow and ice density, and
Water density, the average thickness of the floe can be
calculated on the basis of its hydrostatic equilibrium.
Preliminary testing on Arctic Ocean floes in spring
gave accuracies to within 10 %. There are still many
difficulties to be overcome before the method can be
applied at any time and place, but the start seems
promising.
pretation), in the training of ice observers, and in
climatic and other studies, where sampling techniques
can give excellent results. The permanence of the re-
cord so achieved of an ephemeral medium cannot be ob-
tained in any other way.
At present it is felt that these uses of photography
are not being fully exploited in North America.
Die Entwicklung von Meerwegen in der kanadischen
Arktik blieb hinter dem russischen nördlichen Meerweg
zurück, nicht weil sie schwerer war oder weil in Kanada
Unternehmungsgeist fehlte, sondern weil kein Bedarf für
Solche Wege existierte. Die Errichtung von permanenten
Einrichtungen in der kanadischen Arktik, die eine
jährliche Wiederbelieferung brauchen, hat das Bild
geändert und eine zunehmende Zahl von Schiffen fährt
jeden Sommer in di arktischen Gewässer, die vielen
Kanäle des Archipels mit einjahrigem oder Wintereis und
alterem oder Polereis durchkreuzend.
Um diesen Schiffen beizustehen war ein Eisbericht
und Prognose-system notwendig, das entwickelt wurde.
Die Pionier-arbeit wurde von dem Hydrographischen Amt
der amerikanischen Marine im Jahre 1952 in Baffin Bay
begonnen und wurde spater von Gronland bis zum Bering
Meer erweitert. Nach 1957 hat der Kanadische Meteor-
ologische Dienst den kanadischen Sektor übernommen.
