This book is written for the mariner who wants to learn the concepts of piloting and navigation, and do more than merely follow a closely prescribed set of rules. While the authors have supplied guidance in the practical matters, such as reading the Almanac and carrying out sight reductions (there are reduction forms in the appendices), they have also provided an understanding of the principles so the sailor can invent new methods when required. Readers are expected to be active participants, and there are many exercises designed to help them along the way. What makes this book different from most others is its focus on three methods used in a Harvard freshman tutorial course: confrontation with misconceptions, definitions based on procedures, and the use of imaginary scenarios. The authors feel these are keys to learning, as they are much more powerful than memorization of rules and will prepare the sailor to handle situations that are not in any textbook. Whitney and Wright have directed their writing to the sailor who is interested in the principles but not particularly comfortable with geometry.