3. EQUIPMENT AND INSTRUMENTS 



67 



^ GREEN STATION 



GREEN STATION 



Correction C-d cosCAgAj) 

 d-distance in lanes 



RED STATION 



Figure 18. — Corrections to Raydist distances when 

 three-tower antenna system is used at the red 

 station. 



D^distance in lanes between masts 

 S//=ship's head (true) 

 ^redirection to the Red station 

 A(/=direction to the Green station 



To apply the R^ correction with respect 

 to all variables would be laborious. When 

 the correction is applied, a table of correc- 

 tions to the nearest 0.2 lane should be used, 

 and small course changes required to follow 

 the guide line may be ignored. When the 

 antennas are duplexed at the approximate 

 location of the transducers both Ri and R> 

 corrections are eliminated. 



3-57 Raydist brush recorder. — The brush 

 recorder as used in the Raydist system is an 

 instrument for continuously recording the 

 lane changes as shown on the phasemeter 

 dials. An inked line is drawn on a tape for 

 each dial (Fig. 20). The slope of the line 

 shows whether the lane count is increasing 

 or decreasing and the rate of change. It is 

 especially useful when interference of any 



RED STATION 



Transducer locJt«d xiproaimatelv bdow the foremast 



Figure 19. — Corrections to Raydist distances to re- 

 duce observed positions to location of transducers. 



kind causes the phasemeter to operate 

 erratically. 



During hydrographic operations one man 

 is stationed at the brush recorder. The lane 

 count is marked at the calibration site when 

 the phasemeter dials are set, thereafter ev- 

 ery fifth or tenth lane is numbered. Each 

 position is marked and numbered on the 

 tape. Frequent comparison between the 

 brush recorder and the phasemeter is neces- 

 sary to detect any gain or loss of lane count. 



3-58 Setting phasemeter dials. — Unlike 

 other electronic instruments for determining 

 position, the Raydist phasemeter dials must 

 be set correctly at a known position, and 

 if the lane count is lost it is necessary to 

 return to a known position to reset them. 

 Once the dials have been correctly set, the 

 equipment will automatically keep track of 

 position unless there is serious interference 

 with radio signals or a failure in the 

 equipment. 



The dials may be correctly set, or the er- 

 rors of the dial readings determined by one 

 of several methods: (a) by three-point sex- 

 tant fix plotted on an aluminum-mounted 

 calibration sheet of appropriate scale; (b) 

 at a fixed object of known position such 

 as a pile, beacon, or wharf; (c) by circling 

 a buoy of known position; or (d) when dis- 

 tance arcs curve very slowly by running 

 along a distance arc as determined by a true 

 bearing to a buoy or a fixed object. 



