Review Author: Bill Wallace (wayfarer3130@gmail.com) This book goes over what you would need to know to navigate without various instruments or even without anything and explains WHY you need to do basic navigation - DR even if you have GPS beforehand.
The methods explained are helpful, but this is a book you need to work on before you need it - by the time you need it, you may not have the book available or you may not have the time to learn the techniques.