sea, there have been many conflicting reports on the behavior of this 

 navigational aid as an instrument for ice detection. These reports to- 

 gether with the increased speed of merchant ships and increased usage of 

 radar have emphasized the need for precise and trustworthy information 

 on the reliability of radar as an ice detection instrument. The primary 

 objective of this investigation is to determine the behavior of floating 

 ice to electromagnetic irradiation and thereby assess the efficiency of 

 radar in providing safe navigation through potential ice areas of the 

 North Atlantic Ocean. To attain this goal both field and theoretical re- 

 search were conducted in a controlled quantitative analysis of the various 

 parameters of radar characteristics, target characteristics, meteorology, 

 and sea conditions. 



Shipboard X-band radars of known overall performance were tested on 

 icebergs and berg fragments of different sizes and shapes under varying 

 conditions of sea and weather. Quantitative measurements of reflected 

 power from icebergs and sea waves were made on board the U.S. Coast 

 Guard Cutters Acushnet, Androscoggin and Evergreen; and qualitative 

 observations of the maximum range of detection were made by partici- 

 pating merchant, U.S. Naval, and U.S. Coast Guard vessels. The results 

 and interpretations of these observations together with an evaluation of 

 the effectiveness of anticlutter devices in the discrimination of ice echoes 

 from sea return are presented in this report. 



Previous Work 



The method for quantitative analysis of the ability of radar as an ice 

 detection instrument was devised and field work carried out on the Grand 

 Banks and adjacent iceberg areas during 1945 by the Ice Information 

 Group, Task Group 24.7 [/]. This work was supplemented by investiga- 

 tions in 1946 by the International Ice Patrol [2~\. The reports of these 

 investigations were recently declassified and have been revised and con- 

 solidated by the International Ice Patrol in May 1959 [5]. Qualitative 

 analyses of radar ice reports submitted by Hudson Bay shipping were 

 made by the National Research Council of Canada during 1953 to 1957 

 [4]. The results of these surveys and additional reports from merchant 

 ships transiting ice areas indicate that growlers are inconsistent targets, 

 and that vessels relying on radar for safe navigation through ice infested 

 areas might, in so doing, compromise their safety. It has been established 

 that in calm or slight seas dangerous ice formations of all types should be 

 detected at ranges varying from 10-15 miles for icebergs to 2-3 miles for 

 small growlers and sea ice; however, during moderate and rough sea con- 

 ditions when sea clutter extends beyond 2 miles on the PPI presentation, 

 growlers large 1 enough to cause serious damage to ships might not be de- 

 tected. In view of the recent advances in radar systems and anticlutter 

 circuitry and the need for a quantitative evaluation of radar reliability 

 and anticlutter device effectiveness which could be promulgated to the 

 marine world, the present investigation was undertaken. 



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