Sailing
Due to the convexity of the earth, a ship's upper rigging will be visible at a much greater distance than its lower hull: for example, in clear air a lookout at the top of mast 130 feet (40 m) above the water will be able to see the top of another 130 ft mast from over 24 nautical miles (44 km) away, but will be able to see the full hull of the other ship from only 12 nautical miles (22 km) away.
With a clear horizon, whether a vessel is hull-down or hull-up gives some idea of its distance from the observer, using the line-of-sight formula.
Read more about this topic: Hull-down
Famous quotes containing the word sailing:
“O western orb sailing the heaven,
Now I know what you must have meant as a month since I walked,
As I walked in silence the transparent shadowy night,”
—Walt Whitman (1819–1892)
“Come, cuddle your head on my shoulder, dear,
Your head like the golden-rod,
And we will go sailing away from here
To the beautiful land of Nod.”
—Ella Wheeler Wilcox (1855–1919)
“The Colonel went out sailing,
He spoke with Turk and Jew
With Christian and with Infidel
For all tongues he knew.
“O what’s a wifeless man?” said he
And he came sailing home.”
—William Butler Yeats (1865–1939)