Coordinates and positions
A pair of nautical dividers (single handed dividers) is used to obtain precise coordinates from the chart. This device enables you to take the distance between that particular position and the closest grid line. You then place the dividers on the scale with one end on this grid line, leaving the other end precisely at your coordinate. Do this twice to get both latitude and longitude at the scale on the edge of the chart.Below are some examples.
DISTANCES
To measure the distance between, for instance, these two oil rigs, we will again need our dividers. Remember, we can only use the vertical scale. We
first take a convenient distance like 10' (10 nautical miles) on the
vertical scale using the middle latitude. Then we start walking with the
dividers from the southern oil rig to northern one. Finally, we adjust
the dividers to measure the small remaining part at its own height,
i.e. its own latitude
.
The image shows that the total distance is 37 nautical miles
