Water track and ground track
The direction your vessel is pointing is called the water track and/or heading and represented on the chart by a line we call the water track. This heading is more often than not different from your real course over the ground due to the wind, tides and currents. The real direction that we actually travel over the ground is called the ‘ground track’ or course over ground (COG).
When we plot the water track and ground track on charts we have symbols to differentiate between them. The Water track is represented by one arrow on the direction line and the ground track represented by two. It is important that navigators use a common system so that chart plotting and entries into the ships log book can be understood by anyone who is on watch.