The Autotape system and the Hydrodist system operate in the 10-cm 

 band and use cw phase comparison techniques . Two precisely positioned shore 

 stations are used with each system; these can operate unattended. Automatic 

 plotting equipment increases each system's utility and allows the survey vessel 

 to be positioned with a potential accuracy of 1-3 meters at maximum ranges of 

 25-60 miles . 



The Decca Hi-Fix system utilizes cw phase comparison techniques 

 and ground wave transmission at frequencies in the 2 -mc band. The system is 

 portable and may be used in either the hyperbolic or ranging mode . Automatic 

 track -plotting equipment is available. This system is in use for hydrographic 

 and survey purposes in this country and in Europe. 



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