ICEBERG DETECTION BY RADAR' 



by Thomas F. Budinger 

 (U.S. Coast Guard) 



ABSTRACT 



The behavior of ice to electromagnetic radiation is analyzed to deter- 

 mine the reliability of radar as an iceberg detection instrument. From 

 absolute quantitative measurements, quantitative generalizations, and 

 theoretical considerations the following results were obtained: 



1. Iceberg ice on the Grand Banks has a reflection coefficient of ap- 

 proximately 0.33 and reflects radar waves 60 times less than a ship of 

 equivalent physical cross-sectional area. 



2. The maximum range of radar contact is proportional to the fourth 

 root of the physical cross-sectional area of icebergs. A statistical relation 

 derived from 152 observations shows that growlers normally cannot be 

 detected at ranges over 4 miles. 



3. The Grand Banks and contiguous areas of the North Atlantic Ocean 

 exhibit conditions of subnormal radar propagation during the spring 

 months when fog and ice hazards are most prevalent. 



4. Waves over 4 feet in height might obscure a dangerous growler even 

 with the expert use of the FTC and STC anticlutter devices. If an ice 

 target is not picked up beyond the sea return, it will not be detected at 

 all and a fatal collision might result. 



5. Ice is not frequency sensitive. The response of ice to S- and X-bands 

 is the same. Furthermore, there is practically no difference in the response 

 of sea water to S- and X-bands. 



6. The use of sector scan, trained radar operators, and constant sur- 

 veillance of the radar scope increases the probability of detecting ice by 

 radar. 



7. Commercial radar in common use on the ships of the world today 

 cannot be relied upon for the detection of all dangerous icebergs or frag- 

 ments thereof drifting in the North Atlantic Ocean. This instrument 

 definitely is an aid, but it does not provide an assurance against the 

 presence of all floating ice which might sink a ship upon collision. 



INTRODUCTION 

 Objectives 



Since the inception of radar as a means for providing safe passage 1 at 



1 To be reprinted as Contribution No. 1093 in the Colieeted Reprints oi the Woods Hole Oceanographic Institution 



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