FOREWORD 



Tfie Hydrographic Office recently published a new wave forecasting 

 manual, H. O. Pub. No. 603, prepared by Professor Pierson and his 

 colleagues at New York University under contract with Project AROWA. 

 To supplement this manual the Hydrographic Office herewith presents 

 "Visual Wave Observations," also by Professor Pierson, as an ex- 

 planation of the methods for obtaining wave observations in a manner 

 compatible with the spectral forecasting technique. 



Wave records are of two major types. Those obtained from wave 

 staffs, pressure recorders, and other mechanical devices are accurate 

 and reproducible, but they are also expensive and limited in number. 

 Visual wave observations are subject to error, but they are readily 

 obtained from shipboard as often as desired. In spite of the errors 

 inherent in subjective estimates of wave characteristics, several 

 important types of data can be secured from visual wave observations 

 which can aid in wave forecasting. This report outlines the theory 

 underlying visual wave observations and indicates the data that can 

 be secured from them. 



The Hydrographic Office is actively engaged in the development 

 and operational testing of methods of wave forecasting. In order to 

 increase the usefulness of the operational wave forecasts being issued 

 by this Office, it is necessary to obtain more frequent and accurate 

 synoptic wave reports. It is hoped that this report, which indicates 

 how improved visual observations can be obtained, will encourage 

 observers aboard ships to make observations in the method outlined. 



H. H. MARABLE 

 Captain U. S. Navy 

 Hydrographer 



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