Secondary Port information is provided in Nautical Almanacs such as Reeds’ and also in the Admiralty Tide Tables. These publications can’t possibly give complete Tide Tables for all of the hundreds of small ‘Secondary Ports’ around the coast. Instead they give complete Tide Tables for all of the larger ‘Standard Ports’ like Dover and Devonport (Plymouth). They then also provide ‘Secondary Port Differences’ so that times and heights for any Secondary Port can be easily worked out. LAYOUT OF SECONDARY PORT INFORMATION Secondary Port Time and Height Differences are always presented in a uniform and logical way. Have a look at the diagram below. The top part shows us the presentation of the information in the Almanac or the Admiralty Tide Tables. Underneath we take a look at what that information means. h t t p s : / / c o c k p i t c a r d s . c o . u k / s e c o n d a r y - p o r t s - explained/