Introduction

Well before the modern era, humans have made amazing feats of navigation.  Polynesians were able to find remote islands like Rapa Nui (Easter Island), a needle in the haystack of a vast ocean.   The Norse found, in succession, Iceland, Greenland, and North America.   Gold traders crossed the vast Sahara in camel caravans.  Aboriginals found their way across relatively featureless terrain in what is now Australia.  How did they do this?   How did they guarantee success? 

Back in the day,...