Book excerpt: Today travellers by land, sea and air take accurate navigation for granted but it was not always thus. The author, a highly experienced sailor, sets out to record the development of navigational techniques from the earliest time, five millenniums ago. As explorers started to venture offshore into the unknown they had to rely on the sun and stars for direction. From this pioneers turned to mathematics, astrolobes, sextants and increasing accurate clocks to measure latitude and later longitude. More recently major breakthroughs with electronic navigation, GPS and other satellite systems have revolutionised travel. Focusing primarily but not exclusively on marine navigation, the author weaves a fascinating course through the successes and failures of mankind's quest to explore his world. The result is a thoroughly entertaining and informative work which has no rival.