HOW TO USE TABLE 2

After the courses have been corrected, the differences of latitude and departures are taken from Table 2 for each course and distance and entered in the proper columns of a traverse table.

In Table 2 the courses are from 1 degree to 45 degrees at the top of the page and from 45 degrees to 89 degrees at the bottom of the page. Each degree is a separate table, the distances being from 1 mile to 600 miles, each column limited to 60 miles. If the corrected course is 44 degrees or less, the top of the table must be used and the columns will be in the order, "Dist. Lat. Dep." If the corrected course is 46 degrees or more, the bottom of the table must be used and the columns will be in the order, "Dist. Dep. Lat." If the corrected course is 45 degrees, either top or bottom may be used, as the differences of latitude and departures are the same. That is, if a ship sails 100 miles on the course N. E. she will make 70.7 miles north and 70.7 miles east.

Suppose the difference of latitude and departure for a course N. 31° E. and distance 47 miles is wanted.

Turn to 31° and run down the first (dist.) column to 47'. In the second (lat.) column will stand 40'.3, which should be placed in the N. column of the traverse table. In the third (dep.) column 24'.2 will be found and should be placed in the E. column of the traverse table.

If the corrected course N. 59° E. is taken with the distance 47', it will be found at the bottom and 47' will be found in the first (dist.) column. In the second (dep.) column 40'.3 will be found and should be placed in the E. column of the traverse table. In the third (dep.) column will stand 24′.2, which should be placed in the N. column of the traverse table. Suppose the difference of latitude and departure is wanted for the corrected course N. 31° E. and distance 47.7 miles. In the third distance column on the second page 477 will be

found and from the next (lat.) column 408′.9 and in the next (dep.) column 245'.7 are taken. These numbers are for 477 miles and as the distance is 47'.7 the decimal point must be moved one place to the left, so they will read 40.89 and 24.57. In this work it is not customary and seldom necessary to have these numbers to more than one decimal. For that reason they would read 40.9 and 24.6, the last figures being more than 5 are taken in.

Suppose the difference of latitude and departure is wanted for the corrected course N. 30° 30′ E. and distance 47.7 miles.

To interpolate for the half degree, the differences of latitudes and departures are taken for 30° and 31° and half their sum I will be the result wanted.

Course 30° 30', Dif. lat. 41'.1 and dep. 24'.2.

24'.2= 242.I

To interpolate for the half degree when the distance exceeds 600 miles, enter Table 2 with half of it, or if that is too large, use a third or a quarter; but in any case the largest that falls within the limits of the table is to be used. The mean found must be multiplied by the same number which was used to divide the distance, except when 2 is used as a divisor. Then the sum of the quantities taken for the whole degree on each side of the course will be the result wanted, which is at once entered in the traverse table.

Interpolate for 30' when the minutes of the course falls between 15′ and 45'.

Take from Table 2 the differences of latitudes and departures for the following courses and distances;

Enter Table 2 with the course 81°, which is found at the bottom of the page. With 8 miles in the distance column and reading from the bottom of the page, take out the difference of latitude, 1'.3, and place it in the south column, because the course is south. Also take the departure and place it in the east column, because the course is east.

COURSE NUMBER 2

As this course is 6° 45', 7° is used to enter Table 2 and is found at the top of the page. With 22 miles in the distance column, the difference of latitude, 21'.8 for the south column and 2'.7 for the west column, are found.