# How far off coast is land visible and how long to reach it in 15th century ship?

My character is travelling from mainland Europe to Plymouth in late 15th century. She awakes at dawn on a clear day and can see Plymouth. How close to the coastline would she need to be in order to see the land and how long of the journey would remain at this stage given that conditions are good?

• Welcome to WorldBuilding! If you have a moment please take the tour and visit the help center to learn more about the site. Have fun! – Secespitus Jun 25 '17 at 21:31
• Please clarify which Plymouth you are talking about. – dot_Sp0T Jun 25 '17 at 22:24
• 15th century so it's Plymouth, England. Wikipedia puts the highest point at Roborough with an altitude of 150 meters. Using the formula in the article on Horizon we find that from a height of about 5 meters the Roborough heights can be seen at a distance of about 50 km or 29 miles. Assuming the ships makes 5 knots it will take some 6 hours to reach port, or close enough. – AlexP Jun 25 '17 at 22:25
• And that's 50km/29mi on a clear day allowing that visibility. – Alexander Jun 26 '17 at 17:30
• I have edited a comment that was not entirely polite. I would like to remind people of the Be Nice policy. Constructive criticism is one thing; rude criticism is another. – HDE 226868 Jun 29 '17 at 0:46

Visibility is about 30 miles. Ship speed is largely a function of current speed and air speed. Rowing is less than 5 miles per hour. Under ideal conditions, a sail boat can go about 30 miles per hour. But, usually conditions are not ideal.

Visibility of land would be in the 20 nm range, based on real-life experience as a sailor. There are no mountains in Plymouth, Massachusetts, so that is about all you would get.

An old-timey sailing ship like USS Constitution would be lucky to hit 10 kts. Since this probably isn't a heavily manned warship built for speed, 5kts or under is more likely. So the ~20 miles to land will take you four to six hours, depending on the wind conditions.

If she sees land at dawn, the ship should anchor before noon....assuming they found a good place to anchor. You don't just drop anchor anywhere, and it could take days to find a reasonable spot to anchor along the coast.