Navigating in the 18th Century.

Navigators relied on dead reckoning to plot their course across the oceans and relied on some of these tools to collect data:

Portolan chart.

Portolan charts, often beautifully illustrated, were first developed by the Italians in the 13th Century and were in continued use into the 18th Century. They provided the seafarer with information about ports, the coastline, and shoals. Sometimes towns would be marked with flags indicating the political nature of the area.

Rhumb lines radiating out from as many as 32 points on the compass rose assisted in plotting a course. Also called a windrose, the earliest designs were meant to depict the direction of the eight main winds. A fleur de lys was most often used to point to the north.

Traverse Board

The traverse board was a sort of peg board used to record the progress of the ship. The upper portion was laid out as a compass rose so that a peg could be placed in a hole marking the direction over the course of the half hour watch. The peg holes in the lower portion indicated the speed. In this way, even illiterate sailors could keep an accurate record of speed and direction.

Chip Log

Ship speed over water is measured in knots which derived from the practice of knotting a line at regular increments, tying it to a log, tossing it overboard and counting the number of knots that passed over a specific period of time. Early on the knots were spaced about 42 feet apart, based on the assumption of a 5,000 foot nautical mile. A sand glass was needed to keep track of the time it took for the knots to play out. Shaped like an hour glass, the time duration used was 30 seconds. Thus in 30 seconds, at one knot, the ship travelled 42 feet.