In this section, we are going to talk about the global mapping systems used around the world. It is good to have a basic understanding of all the systems even though you will probably only use one of them for the majority of your navigation. A lot of countries have their own mapping and grid system that varies from country to country. This is based on how they project their part of the spherical planet on the 2D map, because of this all maps have slight inaccuracies from creating a flat map from a curved planet.

There are four global mapping systems to take note of, three for the world and one for the poles, they are:

  • Longitude and Latitude – Most commonly used for marine and aviation but also used for land navigation.
  • Universal Transverse Mercator(UTM) – covers the everything except the north and south poles.
  • Universal Polar Stereographic System(UPS) – Same as the UTM system but for the north and south poles
  • Military Grid Reference System(MGRS) – Similar to UTM and UPS but it uses its own system for labelling

Longitude and Latitude

Latitude

  • Lines of latitude run horizontally around the globe, parallel east to west
  • Used to express how far north or south you are, relative to the equator
  • Latitude is an angular measurement in degrees from 0° at the equator (low latitudes) to 90° at the poles (+90° N for the North Pole or –90° S for the South Pole)
  • Lines of latitude are always the same distance apart – 1° = approx. 110 km

Longitude

  • Lines of longitude run vertically on the globe and converge at the poles
  • Shows your location in an east–west direction
  • Longitude is given as an angular measurement ranging from 0° at the Prime Meridian (also known as the International Meridian at Greenwich, England) to +180°E and –180°W

Longitude and latitude is measured in degrees (°), minutes (‘) and seconds (“). 60 seconds = 1 minute; 60 minutes = 1 degree.

latitude longitude Lines

When you combine a longitude coordinate and a latitude coordinate you can get a precise location anywhere in the world. The Latitude is always shown before the Longitude.

Universal Transverse Mercator(UTM)

The UTM grid system is the most commonly used system after long/lat. Being a grid system it is accurate to within a square of a certain area(depending on the detail of grid reference) unlike long/lat which is a coordinate system that gives an exact location, however, grid systems are easier to read and use.

The UTM divides the world into 60 zones each of 6° and covers everything apart from the south pole(below 80° South) and the north pole(above 84° North).

The zones run from left to right numbered from 1 – 60 with each zone containing 20 latitude bands. The whole system uses the metric system, so kilometres and meters.

UTM System

Take a look at our ‘Reading Grid references’ section to learn more about using a grid system.

Universal Polar Stereographic(UPS)

The Universal Polar Stereographic is another grid system like the UTM System however because the UTM System doesn’t cover the poles the UPS system was created to cover what UTM was missing. This includes below 80° South and above 84°North.

There is one projection for the Arctic and one for the Antarctic with both grids being centred on their respective poles

Military Grid Reference System(MGRS)

The Military Grid Reference System is a grid system that covers the whole globe. It is derived from both the UTM and UPS systems but uses a different labelling system. It uses a series of letters and numbers to denote a grid square. For example, Honolulu is at 4QFJ19285736.

4Q is the Grid
FJ is the identifier of the 100,000m² area
1928 is the easting, the east to west reference
5736 is the northing, the north to south reference

Read Our Reading Grid References section to learn more about Grid systems

MGRS Grid system

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