Jökull - 01.12.1983, Blaðsíða 8

meteorologist-glaciologist, Jón Eythórsson, in the
1930’s (Eythórsson 1949 and 1963). With the public-
ation of Jökull, beginning in 1951, glacier variation
data have been reported nearly every year since.
After Eythórsson’s death, Sigurjón Rist, the Icelandic
hydrologist-glaciologist, assumed the responsibility
for annual reports. In 1951, Eythórsson had reported
on the position of 26 outlet glaciers or glacier
margins of 8 different glaciers (Eythórsson 1951). In
1977, Rist reported on 40 of 61 monitored outlet
glaciers or glacier margins of 11 different glaciers.
Although the annual monitoring of the position of
40 different glacier termini or ice cap margins re-
presents a significant effort, it includes only about
12 percent of the 330 named individual glaciers and
named and unnamed outlet glaciers of the various
icecaps in Iceland which potentially could be
monitored annually. It should also be noted that the
current position measurements are ”spot” mea-
surements and represent only a ”sample” of the
overall state of Iceland’s ice caps.
MAPS OF ICELAND'S GLACIERS
Pálsson’s maps (1795) of Vatnajökull (Klofajök-
ull) in 1794, Eyjafjallajökull (including Mýrdalsjök-
ull) in 1795, Langjökuli in 1792, and Hofsjökull
(Arnarfellsjökull) in 1794 were the first attempt at
the scientific mappingoflceland’s glaciers. Thorodd,-
sen’s ”Geological Map of Iceland” (1901), which
was based on field surveys (1881-98) and Gunnlaugs-
son ’s map (1844), portrayed nearly all of the glaciérs
of Iceland in their approximate geographic
location. Both Pálsson’s and Thoroddsen’s maps of
glaciers however, can really only be used in a
qualitative sense (seeTable 1). For example, Pálsson
referred to present-day Ok (with a small glacier) as
Okjökull, and Thoroddsen (1901 and 1906) mapped
Glámujökull (230 km2) on present-day Gláma (no
present glacier).
The modern mapping of Iceland’s glaciers was
begun by the Danish Geodetic Survey in 1904, and
the plane-table surveys continued until just before
World War II, resultingin complete 1:250,000- and
l:100,000-scale maps and some l:50,000-scale
maps of Iceland. The U.S. Army Map service com-
pleted new 1:250,000- (Series C562) and 1:50,000-
scale (Series C762) maps of Iceland after World
War II, using aerial photogrammetric surveying
techniques. The U.S. Defense Mapping Agency
and the Icelandic Geodetic Survey are currently
preparing a new series (C761) of l:50,000-scale
maps of Iceland. The Icelandic Geodetic Survey is
currently preparing a 1:10,000-scale orthophoto-
map series. The Icelandic Geodetic Survey also
publishes special-purjxtse maps at various scales, in
addition to periodic revisions of the 1:100,000- and
1:250,000-scale Danish Geodetic Survey maps.
IMAGING OF ICELAND'S GLACIERS
Although aerial photographs of the glaciers of
Iceland had been used by some scientists, such as
Iwan (1935), who published oblique aerial photo-
graphs of glaciers taken from a Zeppelin, the
Danish Geodetic Institute acquired the first aerial
photographs of Iceland’s glaciers in 1937 specific-
ally for topographic mapping (Norlund 1938). Six
oblique aerial photographs ofVatnajökull, taken by
the Danish Geodetic Institute in June and August
1937 from 3600 m, were published by Ahlmann
(1937).
In 1944 and 1945, the U.S. Army Air Force
acquired vertical aerial photographs ofmost of Ice-
land. After World War II, the Icelandic Geodetic
Survey assumed responsibility for acquisition of the
vertical aerial photography of Iceland to support
map revision needs and to support special map
projects for other agencies (for example geothermal
research, site planning for hydroelectric power
projects, road construction, etc.). In 1956 and from
1959 to 1961 (Project 55-AM-3), the U.S. Air Force
rephotographed most of Iceland to support a new
l:50,000-scale map series (Series C761).
There have been a number of miscellaneous
aerial surveys of Iceland since 1960, mostly in sup-
port of special research projects. The U.S. Air
Force, theU.S. Navy, and theNational Aeronautics
and Space Administration (NASA) all conducted
limited aerial surveys in Iceland during the 1960’s
and 1970’s.
Beginning in September 1972, the first in the
Landsat series ofsatellites (three more were launch-
ed in 1975, 1978 and 1982, respectively), began to
acquire Landsat images of Iceland, providing a new
source of information about Iceland’s glaciers.
During 1973 the best images of the ice caps of
Iceland were acquired, although a few excellent
images have been acquired in recent years by
Landsat receiving stations in Canada and Sweden.
Landsats 1, 2 and 3 multispectral scanner (MSS)
images have a maximum picture element (pixel)
resolution of about 80 m; Landsats 1 and 2 return
6 JÖKULL 33. ÁR