In this video, we talk you through how to calculate tidal flow rate and direction using a tidal atlas and the tide tables in the 2020 Reeds Tidal Almanac.
In other articles, we talked about how we apply variation and deviation. In this article we explain how we establish variation on an older paper chart where variation has been changing over time.
This video explains how you calculate variation in any given year on an older chart. If you want to know how to apply variation, click here.
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For a map to be useful in helping to navigate and plan a voyage (us sailors call them charts) it must be properly understood and be accurate for its purpose. Charts are physical (or electronic) representations of the physical characteristics of the earth & the water on it. They are a projection of a curved surface (the earth) onto a flat one (such as a sheet of paper or computer screen).
It's necessary to make some adjustments to how this information is presented so that this projection can be done whilst still making it a useful and navigationally accurate representation of the surface of this spherical planet.
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All content created by Mark Burkes, an RYA Yachtmaster™ Ocean Instructor. 200,000 miles logged over 30 years. Learn more...
All charts used in our videos and on this website are used under copyright from HMCO licence no. 35358. Not for navigational purposes.