sdenton4 parent
Using this method repeatedly to guess how far you've moved over the course of days is, historically, a fantastic way to crash into the side of France in the middle of the night.
Well the other problem is knowing where you are. The sun/stars can give you latitude. Longitude was nearly impossible until the advent of the marine chronometer in the latter part of the 18th century, and not "standard" on ships until the mid-1800s. There were earlier versions, which had poor accuracy and were not much better than dead reckoning