THAT’S RIGHT FOLKS.... MATH! Navigation Calculations

It takes an average time of 24 hours for the Earth to rotate 360 degrees. If you divide the number degrees in a circle by the number of hours in a day, we find that the Earth turns 15 degrees each hour. So, 360° / 24 hours = 15° per hour We can take this a step further and state that the Earth turns one degree in four minutes. 1 hour = 60 minutes / 15° = 1 degree per 4 minutes

Minutes and seconds sometimes follow latitude and longitude measurements to more accurately pinpoint a location. Each degree can be divided into sixty minutes, usually indicated by a single quotation mark (ex. 5'). For example, 90°15’N. Each minute can be divided into sixty seconds, indicated by a regular (double) quotation mark. For example, 90 o 15’5”N.

On land, distance is expressed in kilometres or statute miles (USA). At sea, distance is measured in nautical miles. One nautical mile is equal to 1’ of latitude. 1 nautical mile = 1.15 statute miles = 1.85 kilometres = 1 minute of latitude 1°latitude = 60’ latitude = 60 nautical miles

Example: You are 20 nautical miles from your dock. How many kilometres distance are between you and home? 20 nautical miles X 1.85 km = 37 km nautical mile Example: If you had to travel 2 o in your yacht, how many kilometres would this be equivalent to? 2 degrees X 60 nautical miles X 1.85 km = 222 km degree nautical mile

The unit of speed used at sea is the knot. One knot is defined as 1 nautical mile/ hour. 1 knot = 1.85km/hr Example: If a boat is travelling at a speed of 25 knots, how fast is this in km/hr? 25 knots X 1.85 km/h = km/h 1 knot

Depth soundings are measured in fathoms where: 1 fathom = 1.8m = 6 feet Example: If you measure the water off your raft and it measures 10 feet, what is this in fathoms? 10 feet X 1 fathom = 1.67 fathoms 6 feet