Book excerpt: Radar and ARPA Manual focuses on the theoretical and practical aspects of electronic navigation. The manual first discusses basic radar principles, including principles of range and bearing measurements and picture orientation and presentation. The text then looks at the operational principles of radar systems. Function of units; aerial, receiver, and display principles; transmitter principles; and sitting of units on board ships are discussed. The book also describes target detection, Automatic Radar Plotting Aids (ARPA), and operational controls of radar systems, and then discusses radar plotting. Errors associated with the true-motion presentation; accuracy and errors of manual plotting; radar plotting aids; and regulations for preventing collisions at seas as applied to radar and ARPA are described. The book also underscores the accuracy and errors of ARPA. The test scenarios; errors generated in the radar installation; classification of ARPA error sources; and errors in displayed data and interpretation are explained. The manual is a good source of information for readers wanting to study electronic navigation.