Military/Info Home Page Freebie Menu Page

Finding the Distance of Objects at Sea, in Statute Miles (1848)

From Military/Info Publishing

Height in feet  Distance in Miles   Height in feet Distance in Miles 
.582* 1 30 7.25
1 1.31 35 7.83
2 1.87 40 8.37
3 2.29 45 8.87
4 2.63 50 9.35
5 2.96 60 10.25
6 3.24 70 11.07
7 3.49 80 11.83
8 3.73 90 12.55
9 3.96 100 13.23
10 4.18 150 16.20
11 4.39 200 18.72
12 4.58 300 22.91
13 4.77 400 26.46
14 4.95 500 29.58
15 5.12 1000 32.41
16 5.29 2000 59.20
17 5.45 3000 72.50
18 5.61 4000 83.70
19 5.77 5000 93.50
20 5.92 1 Mile 96.10
25 6.61    

* 6.99 inches.

The difference in two levels is as the square of the distance. Thus, if the height is required for 2 miles, 1: 2 :: 6.99 : 27.96 inches; and if for 100 miles, 1 : 100 : : 6.99 : 1.103 + miles.

For Geographical miles, the distance for one mile is 7.962 inches.

Example.-- If a man at the foretop-gallant mast-head of a ship, 100 feet from the water, see another and a large ship (hull to), how far are the ships apart?

A large ship's bulwarks are, say 20 feet from the water.

Then, by the table, 100 feet = 13.23  
, 20 feet = 5.92  
Distance = 19.15 miles

Note. -- 1/13 should be added for horizontal refraction.

From: Engineers' and Mechanics' Pocket-Book (5th edition) by Chas.H.Haswell, Engineer in Chief, U.S.Navy; New York: Harper & Brothers (1848), pages 21-22

Note:
1  The above has been brought to you by Military/Info Publishing (Home page).
2. Military/Info Publishing specializes in the last 200 years of historical military technology. We are sort of the lost and found department of military manuals and articles on the web.
3. Now in business for 17 years, on the web for 12, adding around 50 items a month to our lists.
4. Military/Info Publishing has over 11,000 other manuals, articles, and books for sale. Organized into over 200 subject heading (Subject Index).

Military/Info Home Page Freebie Menu Page