Navigation Unravelled – The Course to Steer made easy.

Navigation Unravelled – The Course to Steer made easy.

29/09/2018 1 By Mark Sanders

I’d like to share my recent idea and findings on simplifying course to steer for us.

New students (and older ones) virtually always confuse the construction of course to steer (CTS) with estimated position (EP) despite us stressing EP is position fixing and CTS is constructing a diagram to find what angle to steer into a tide to counter it.
Typically we forget to draw the tidal vector from the start position. Even after intense theory and repeated examples we hold our head in our hands as the tidal vector gets put on at the wrong end.

So, what I now do when teaching CTS is to construct the diagram on a nearby compass rose.



Step 1. Draw your intended ground track on the chart and transfer it to a near by compass rose. easy to do as the numbers are printed all around the rose.






Step 2. Put tidal vector on from centre of the rose.

(There is a natural tendency to work from the centre and in stressing that it’s a diagram we are constructing, drawing lines over the land doesn’t cause so much concern)

Step 3. Boat speed applied at the end of tide. (bit of rhyme there to help remember next time)


Also stops us doing the classic mistake of drawing from the end of the tidal stream vector straight to the waypoint.

Using the scale on the side of the plotter (inches and 10ths) for distance makes it a very quick way of coming up with the right answer.

Hope that’s of interest