Basic Radar Plotting. Ranger Hope © 2008. ______________________________

*Plotting terms and abbreviations:

The application of simple geometry on a plotting sheet, a paper record of the radar display (PPI) over an interval of time, will enable you to determine the collision risk and safe action. The standard abbreviations drawn on a plotting sheet are:

C -The centre of a radar plotting sheet. O -The position of the initial report of a target on the PPI. A -The position of a final report after an interval of time. P -A point on the extension of line OA that passes closest to C. CPA - The predicted closest point of approach of the paint. TCPA - The predicted time of the closest point of approach. WO - Way of Own-a line representing your course and speed. WA - Way of Another-a line representing the target’s course and speed. ______________________________

For an excellent, in-depth explanation for calculation of aspect angle and its role in collision avoidance, see 'Navigating Using Radar'. 2nd Edition © North Bay Power and Sail Squadron North Bay, Ontario. Chapter 8, Section 5.1.3. P71.