Many people struggle to learn Secondary Ports but this simple graphic method shows how simple Secondary Port Calculations can be. This A4 encapsulated sheet will make life so much easier.

Side one explains how the information that you need is laid out and what that information means. It then shows a worked example of Time Differences and side two has a worked example of Height Differences. Side two also has plenty of space for your own calculations.

Matt encapasulation means that a 2B pencil may be used directly on the plastic.