## 1. Parallel Sailing

Parallel sailing means sailing along a parallel of latitude which also means maintaining a true course of east 090 or west 270.

The distance sailed would be the departure at that latitude.

Departure / D’long = Cos Lat

## 2. Plain Sailing

we can assume small areas of the earth surface are flat and can apply trigonometry without any error, But after 600 nm we cannot do this.

Departure / D’long = Cos (Mean LAT)

Tan (Co) = Dep /d’lat

## 3.Mercator Sailing

For sake of convenience in

Rhumb line – Rhumb line is a line that cut all meridians at the same angle. All lines drawn are Rhumb line on a Mercator chart.

Characteristics of a Mercator Chart

- Equator appears as a straight line.
- All meridians appears as st. line parallel to one another.
- meridians cross equator at 90degree.
- Distance between consecutive meridians are constant.
- Polor regions do not appear.
- Parallel of latitude would appear as a stright lines Parallel to one another.
- Distance between parallel of lats increases as latitude increases.
- One minute of d’long is same size in all parts of the chart.