A warning about using chart plotters at the SW Sunk swatchway at the present time

Roger Gaspar has written an article about SW Sunk swatchway

Our 2026 survey showed that the swatchway has moved significantly, especially compared to 2024.  The new chartlet is posted up on the noticeboard and can be downloaded FREE at:  https://www.crossingthethamesestuary.com/page29.html.  Because of the move, it is important to provide some additional information relevant to using a chart plotter, or indeed a current paper chart.