spectral-zones, viz. green (0.5 - 0.6 um), red (0.6 - 0.7), and 
  
the short-wavy infrared bands 0.7 - 0.8 and 0.8 - l.l um; 2:0 a 
three-colours TV-camera with a resolution of about 80 m, working 
on the spectral-bands 0.475 - 0.575. 0.58 - 0.68 and 0.69 - 0.83 um. 
At the receiving stations the video-band data were transferred to 
a 70 mm film and enlarged to photographic pictures of about 
23 x 23 cm, on the scale of 1:1 000 000. On a comparison with 
topographic maps the correspondence was striking. 
4.5.2 Southern Ice Limit Charts 
  
After the XIIth International Congress in Ottawa, July-August 
1972, the author of this report had the opportunity to visit the 
Canadian High Arctic for some weeks' arctic research and ice 
reconnaissance. From there he visited the US Fleet Weather 
Facility at Suitland, Washington, D.C., for the purpose of Ice- 
chart studies. 
There they make excellent ice charts on the basis of satellite 
pictures, air reconnaissance - photographic as well as visual and 
radar reconnaissance - and observations from ships, ice islands and 
coastal stations, etc. Some of these very lucid ice charts show 
the ice situation in the Northern Hemisphere. They are published 
weekly, and called "Southern Ice Limit'"-charts. Others are prognostic 
charts, called "Western and Eastern Arctic 30-day Forecast", pub- 
lisched twice a month. 
The first-mentioned ice charts are divided into two groups, Western 
and Eastern Arctic Analysis, respectively. The westerly "Southern 
Ice Limit"-charts show the ice conditions between about 85° W. and 
85° E., the easterly ones between about 125° E., and 125? w. 
The varying ice concentration over a defined area is given as the 
ratio in oktas of the sea surface actually covered by ice to the 
total area of sea surface, both ice-covered and ice-free.