How are dividers used by a maritime navigator to predict a vessel's position following a change of heading?

Question

How are dividers used by a maritime navigator to predict a vessel's position following a change of heading?

Answer 1

A bit more info to Marks answer:- Dividers are used to measure distances as the flat charts do not follow the earths curvature and a simple scale is not accurate all over the chart so the dividers are used to measure using the nearest printed scale on the chart. Also dividers are easier to use on a boat being tossed all over the place in a heavy sea rather than a "scale rule"

Headings are plotted using parallel rulers to work from the nearest compass rose printed on the map.

Answer 2

The two previous answers are correct in them selves, however the scale on a Mercator Chart, the type used for navigation, is to be found by measuring up the side of the chart on the latitude scale with the centre of the range being at the mean latitude between the positions.

Answer 3

Dividers are used to measure the distance scale on the chart, and with heading and speed information a position estimate can be made. Example, if you are making 10 knots and heading north and then turn east, the navigator would know that at 10 knots the vessel moves 10 nautical miles in 1 hour. If he adjusts the dividers to match 10 nautical miles on the chart scale and then uses them to mark the chart from the point of your turn to a point on the new heading line thats where the vessel will be in one hour.