6 EXPLANATION OF TABLES 
TABLE 10.—DISTANCE BY VERTICAL ANGLES (distance greater than 5 miles). 
This table gives the distance greater than 5 miles of an object of known height by the angle it 
subtends at the position of the observer. The table comprises heights from 400 to 15,500 feet 
above the sea and distances from 6 miles to 85 miles. It contains correction tables for refraction 
and dip, both of which are subtracted from the observed angle after applying the index correction 
of the sextant. Aircraft using the bubble sextant correct the observed altitude for refraction only. 
This table is used for angles of elevation, or for those cases where the height of object is greater than 
height of observer. 
Exampte: The altitude of a mountain top 15,000 feet high was observed which gave by sex- 
tant an elevation of 1°40’; I. C.+1/; height of eye 35 feet, estimated distance 60 miles. Find the 
required distance. After applying the index correction of plus 1’ the altitude is 1°41’. From the 
table, the correction for Dip is —5’.8, and the correction for refraction is —4’.4 or a total of —10’.2. 
This correction subtracted from 1°41’ gives an angle of elevation of 1°30’.8. Enter table ordi- 
narily with the difference between the height of object and height of eye, but when the height of 
eye is relatively low this may be disregarded. Therefore under the column for 15,000 feet find the 
angle nearest 1°31’. By interpolation the distance away is found in the side column to be approxi- 
mately 67.6 nautical miles. 
It must be noted that observed bearings are the same as great circle bearings and are not the 
same as mercator bearings taken from the chart. The mercator bearing requires a correction 
similar to the correction of a radio bearing. In most cases this correction can be disregarded, unless 
the mountain is very far away or the vessel is in high latitudes. ; 
TABLE 11._HORIZON ANGLES. 
This shows the distance in yards corresponding to any observed angle between an object and the 
sea horizon beyond, the observer being at a known height. 
The method of use is explained in Chapter IV. 
TABLE 12.—SPEED TABLE. 
This table shows the rate of speed, in nautical miles per hour, of a vessel which traverses a 
measured mile in any given number of minutes and seconds. It is entered with the number of 
minutes at the top and the number of seconds at the side; under one and abreast the other is the 
number of knots of speed. 
TABLE 13.—TIME—SPEED—DISTANCE TABLE. 
This table shows the distance in nautical miles steamed in any part of an hour from 5 knots 
to 37 knots. It is entered with the number of minutes at the side, with speed in knots at the top, 
abreast of one and under the other is found the distance in nautical miles. 
TABLE 14.—CONVERSION TABLES FOR NAUTICAL AND STATUTE MILES. 
TABLE 15.—CONVERSION TABLES FOR METRIC AND ENGLISH LINEAR MEASURE. 
TABLE 16.—CONVERSION TABLES FOR THERMOMETER SCALES. 
TABLE i7.—REDUCTION OF LOCAL CIVIL TIME TO STANDARD MERIDIAN TIME. 
This table contains the reduction to be applied to the local time to obtain the corresponding 
time at any other meridian whose time is adopted as a standard. The results are given to the 
nearest minute of time only; being intended for the reduction of such approximate quantities as 
the time of high water or time of sunset. 
TABLE 18.—DIP OF SEA HORIZON. 
This table contains the dip of the sea horizon, calculated by the formula: 
D=58''.8VF, 
in which #=height of the eye above the level of the sea in feet. 
It is explained in Chapter X. 
TABLE 19.—DIP SHORT OF HORIZON. 
This table contains the dip for various distances and heights, calculated by the formula: 
p=3a+0.56514 x5, 
in which D represents the dip in miles or minutes, d, the distance of the land in sea miles, and h, the 
height of the eye of the observer in feet. 
