Nautical chart navigation is the cornerstone of passage planning. Every leg of a voyage requires converting a desired track to a compass course, accounting for the local magnetic variation, the vessel's compass deviation on that heading, and any current that will set the vessel off course during the passage.
The course correction triangle
When a current exists, a vessel must steer a different course than the desired track in order to actually travel along that track. The three components of the triangle are:
- Desired track (course made good) — the direction from departure to destination
- Current vector (set and drift) — the direction and speed of the current
- Compass course to steer — the heading the vessel must maintain to counteract the current and stay on track
Solving the triangle gives both the course to steer and the speed made good along the desired track. The Chart Course game presents these triangles in graphical form and asks players to solve them by positioning vectors correctly — reinforcing the geometry rather than just formula memorization.
Running fixes and position lines
A running fix is used when only one landmark is available for bearings. Take a bearing on the landmark, note the time; travel a known distance on a known course; take a second bearing. Advance the first bearing (position line) along the vessel's track by the distance traveled to cross it with the second bearing — the intersection is the running fix. The Sat Nav Fix game cross-checks GPS positions against visual bearings and depth contours, illustrating why multiple sources of position information are always preferred.