How good is the fix?

• A small cocked hat does not prove a good fix. A constant error, like an unapplied index error or a wrong height of eye, moves every line by the same amount and can leave a tidy, wrong triangle.
• Bodies spread right round the horizon cancel a constant error: the hat grows but its center stays put.
• A running fix is only as good as the course and speed between the sights. Tidal streams and leeway move it.
• Compare the fix with your DR. A big jump means a mistake somewhere: check the time, the date and the signs first.

The plotting practice uses sights that are already reduced, so it is all about the sheet. Use the zoom button to place your fix precisely; the readout gives its bearing and distance from the DR.

When you take real sights, Work your own sight (under Tools on the course page) reduces each one step by step, so you can check your own work, and plots the fix from your lines.