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TYPES OF NORTH (Land Navigation Using A Map & Compass)
The article below is an extract from the Leading Cadet Resource Book 2019-2020
Please note this information is subject to Copyright 2018 Thomas Grocott. Not for reproduction. Thomas Grocott has asserted his right to be identified as author of this work in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved. Some images in this publication are Crown Copyright and contain public sector information licensed under the Open Government Licence v3.0.
| When map reading there are three types of north that need to be considered; grid north, true north and magnetic north. Unfortunately, they are all found in different locations. |
Grid North
• The world has been divided into horizontal and vertical lines to make it easier to navigate.
• The east-west lines are lines of latitude and the north-south lines are lines of longitude.
• These lines are curved, getting closer together nearer the top and bottom of the Earth to take account for the curve in the earths surface. They meet at the northern and southern tips of the globe.
• The imaginary point where the lines of longitude meet at the top of the globe is known as grid north.
True North
• True north is at the geographic north pole. There is no physical ‘north pole’ because it is located in the middle of the artic ocean and is always covered in moving sea ice. However, its exact location is known and stays the same.
• True north is not the same as grid north. The difference between true north and grid north can be as much as 2°.
Magnetic North
• The Earth has its own magnetic field. When a compass points to north it points towards magnetic north.
• Magnetic north is not the same as true north or grid north. In fact, magnetic north is located in Northern Canada. It changes slowly over time.
• In the UK in 2018 magnetic north is between 0° and 2° west of grid north.
• The difference between grid north and magnetic north is known as the Grid Magnetic Angle (GMA).
The Grid Magnetic Angle
• The grid magnetic angle becomes important when you start navigating using a map. A compass uses magnetic north, but a map uses grid north.
• All Ordnance Survey (OS) maps will tell you what the grid magnetic angle is for that particular map.
• The difference between magnetic north and true north is called magnetic variation, but we don’t normally use this when navigating.
• The difference between the types of north are illustrated below:
The differences between norths illustrated on a satellite image.
