14-179 Zero Point (XI).— The zero point 

 is determined bv averaging tlie sum of columns 

 VI and VIII ofGEK-1 sheet. 



14-180 Average Base-Course Signal Mag- 

 nitude (XII). — This quantity is (h'termined by 

 first computing the auxihary quantity Y, which 

 is one-half the sum of columns IV and X minus 

 column XI. 1' of course may be a negative 

 number. XII is the absolute (positive numeri- 

 cal) value of Y. 



14-181 Average Base-Course Signal Direc- 

 tion (XIII). — This quantity is the same as that 

 in column III, if Y (section 14-180) is positive 

 or zero If Y is negative or zero, then it becomes 

 column III ± 180° (whichever leads to an angle 

 between 0° and 360°). 



14-182 Average Fix-Course Signal Magni- 

 tude (XIV). — This quantity is determined by 

 subtracting column XI from column VI and 

 taking the absolute (the positive numerical) 

 value of the result. 



14-183 Average Fix-Course Signal Direc- 

 tion (XV). — This quantity (1) is the same as 

 column V if column VI is algebraically greater 

 than or equal to column VIII; or (2) it is the 

 same as column VII if column VI is algebrai- 

 cally less than or equal to column VIII. 

 Remember that —5 is less than —2, and that 

 ~2 is (jreater than —5. 



14-184 Resultant Signal Vector Magnitude 

 (XVI). — This quantity is the positive square 

 root of the sum of the squares of the Average 

 Base-Course Signal Magnitude (XII) and the 

 Average Fix -Course Signal Magnitude (XIV). 



14-185 Resultant Signal Vector Direction 

 (XVII). — The auxiliary angle A must first be 

 determined. Divide the Average Fix-Course 

 Signal Magnitude (XII) by the Average Base- 



Course Signal Magnitude (XIV). The result 

 is the tangent of A. From a tangent table 

 tabulated in 1-degree increments (3-decimal 

 accuracj' is adequate) find the angle A, to the 

 nearest degree, whose tangent is the above 

 quotient. Angle A is added to the Average 

 Base-Course Signal Direction (XIII) if column 

 XV is 90° greater than column XIII. Angle 

 A is subtracted from XIII if column XV is 

 90° less than XIII. This value is the resultant 

 signal vector direction (XVII). 



14-186 Alternate Method for Determining the 

 Resultant Signal Vector Direction. — The aver- 

 age base and fix course vectors may be plotted 

 on a Mark 3A Plotting Board or on any vector 

 plotting paper, and the resultant signal vector 

 determined graphically by the completion of 

 the parallelogram method. 



14-187 Correction to Standard Isodynamic 

 Line (XVIII).— This quantity is 1.04 multiplied 

 by the quotient of the Standard Vertical 

 Magnetic Intensity (I) divided by the Local 

 Magnetic Intensity (II), which are given on 

 GEK-l sheet. 



14-188 Current Velocity Speed in cm./sec. 

 (XIX). — This is the Correction to Standard 

 Isodynamic Line (XVIII) multiplied by the 

 Resultant Signal Vector Magnitude (XVI). 



14 189 Current Velocity Speed in Knots 

 (XX). — To obtain the current velocity in 

 knots, multiply the Current Velocity Speed in 

 cm./sec. (XIX) bv 0.0194. 



14-190 Current Velocity Direction (XXI).— 

 To obtain the current velocity direction in 

 degrees true, add 90° to the Resultant Signal 

 Vector Direction (XVII) when in the northern 

 magnetic hemisphere. Subtract 90° from the 

 Resultant Signal Vector Direction when in the 

 southern magnetic hemisphere. 



OCEANOGRAPHIC LOG SHEET L, PRNC-NHO-1364 



(New 8-52) 



INSHORE SURVEY STATION SHEET 



14-191 GENERAL REMARKS.— The L- 



sheet is used only for special inshore area sur- 

 veys. It is a station log sheet for temperature, 

 salinity, density, wind, sea and swell, and Secchi 

 disc observations. This log sheet, combines 

 some of the features of the A-, D-, and E-sheets, 

 and the Shipboard Wave Observation Log. 

 It is used only when instructions for a cruise 

 specifically so state. 



14-192 THE LOG SHEET.— A sample log 

 sheet is shown in figure 14-10. Print all 

 entries accurately and neatlJ^ 



14-193 The Log Sheet Headings.— Entries 

 in the log sheet headings are made as given 

 below. 



14-194 Vessel. — Give the name and num- 

 ber of the ship on each sheet. 



H. O. 607 



153 



