Compass Rose
The large circle in the center is obviously a compass rose, although it has other purposes as well. The scale of the plotting sheet is (normally) such that the radius of the compass rose is 60 nm = 1 degree.Latitude Lines
The scale of the plotting chart is such that the distance between the horizontal lines is one degree of latitude. As you can see, the vertical line has been marked in one-minute increments. Also remember that one minute of latitude equals one nautical mile (approximately).It's a good idea to mark the central latitude line with your working latitude
Longitude Lines
There are no other vertical lines since this chart is intended to be used at any latitude. At the equator, the longitude lines would have the same spacing as the horizontal lines. As you move away from the equator, the longitude lines are drawn progressively closer together.The first thing you do when using a plotting sheet is to draw in some longitude lines. The easiest way to do this is to use the compass rose as your guide. Starting at the most horizontal points of the rose (90° and 270°), count up and down the number of degrees of your latitude. For example, when working at latitude 54°, you would count up and down from the 90° and 270° points to find 36°, 144°, 216° and 324° respectively. Mark these points. Draw two vertical longitude lines through these two pairs. You now have a rectangular-projection map of your local area. Feel free to draw in some sea monsters and mermaids if it makes it look more like a map to you.
See this picture to see a plotting sheet with working lines added for latitude 54°.
Scale
This scale deserves some special attention. The plotting sheet
is a map, and all maps need some scales. The marks on the central
vertical line represent nautical miles (as well as minutes of
latitude.) Measurements anywhere on the map may be made by using
dividers to transfer distances to this scale.
This scale in the corner is used to measure minutes of longitude. To use, find your working latitude in the scale on the right edge and draw a horizontal line through the scale. Now, minutes of longitude may be measured along this horizontal line.