Data Recovery 



Positioning 



40. Positions were obtained for all measurement sites with LORAN, sup- 

 plemented when possible by visual and radar bearings to identifiable shore 

 features. The LORAN was calibrated for local variance by occupying known lo- 

 cations with the boat and recording both time differences (TD) in microseconds 

 and the LORAN 's automatic conversion to latitude and longitude. The offset 

 from true position was entered into the microprocessor-controlled LORAN for 

 automatic adjustment of calculated position. After this calibration, known 

 positions were again occupied on each day of operation. Thus, a correction 

 factor for each region of the harbor, valid for each day's atmospheric condi- 

 tions, was obtained and allowed an improvement from LORAN 's normal error of 

 ±300 to ±30 ft. 



Tide gages 



41. Of the eight tide gages deployed, seven were recovered. One of the 

 redundant gages, number 5, had not been recovered at the time of this report's 

 preparation; its acoustic transponder did not respond to surface interroga- 

 tion, and a side -scan sonar search failed to show an identifiable target. Two 

 other gages were located using side-scan and "sweeping" with a chain suspended 

 between two vessels when acoustic releases failed to operate, but extensive 

 diver searching verified that this gage was not in the immediate area. Since 

 the subsurface float provides an easy target for both search methods, it seems 

 likely that the gage and mount (or at least the buoy) were the victims of an 

 encounter with a deep draft vessel. In that event, the gage may have been 

 dragged off station, but could still be in the general harbor area. An 

 expanded search of the harbor and surrounding offshore waters was conducted 

 using the acoustic interrogator in subsequent months without success. 



42. Tide Gage 2 (TG2) experienced a sudden electronic failure partway 

 through its deployment. Data were recorded from installation on 10 June 

 through 20 August. Tide Gage 4 (TG4) experienced a tape drive failure that 

 made the entire data set unrecoverable. Tide Gage 8 (TG8) exhibited a drift 

 in amplitude and phase because of electronic failure. Portions of the data 

 set are recoverable, but can only be used for frequency analysis unless some 

 arbitrary correction is made to the time axis. The remaining four gages had 

 no failures, and their locations coincided with the requirements for two 



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