NWP105A: Use maps, plans and drawings

Location

Latitude and longitude

You can locate a feature on a map using a map's grid system and coordinates. Locations of maps can be found using:

Latitude and longitude are imaginary lines used to give you an exact location on the Earth's surface. Find out more about these by clicking on the images below.

REMEMBER: When reading a map you always give the latitude reading first.

  • globe with lines of latitude marked
  • globe with lines of longitude marked
  • globe with hemispheres marked

1. Lines of latitude run parallel to one another and are shown as horizontal lines on maps, numbered from 0 - 90 degrees going either north or south from the centre.

The equator is the starting point for all lines of latitude at 0 degrees. It is the longest line of latitude as it runs around the centre of the planet where it is widest.

The equator also divides the globe into northern and southern hemispheres.

The numbering increases as you move away from the equator until you reach the north pole (90°N) or the south pole (90°S).

2. Lines of longitude are shown as vertical lines on a map. They are also numbered in degrees starting with 0.

The starting point for longitude is a line known as the Prime Meridian, and it runs from pole to pole through a place called Greenwich near London.

The numbers for longitude increase the further they are from the Prime Meridian, up to 180 °.

Longitude lines are not parallel, as they meet at the two poles.They divide the Earth like orange segments.

3. Hemispheres divide the globe into halves. The halves can be from north to south or east to west.

The starting points (0 degrees) for each hemisphere are the Equator (north-south)and the Prime Meridian (east-west).

As the starting points are always the same, it is important to know which hemisphere an area is located in when reading topographic maps.

Australia, for example, is in the southern and eastern hemispheres, so on an Australian topographic map, latitude is read from top to bottom and longitude is read from left to right.


Reflect:

Can you find out which line of longitude your part of Australia lies across?

Alphanumeric grids

Grid referencing is another way of finding or providing coordinates for location on a map.

There are two types of grid referencing used:

  • alphanumeric grids (letters and numbers)
  • numerical grids (numbers only).

Alphanumeric grids use grid squares to provide a reference. For example, on a road map you will usually find letters going from left to right across the top and numbers going from the top to the bottom. Readings are given with the letter first (A6, E2).

Grid referencing

Numerical grids are made up of eastings and northings.

Eastings increase in value towards the east. They are shown as vertical lines on maps. Northings increase in value towards the north. They are shown as horizontal lines on maps.

grid map with northings and eastings marked

Usually two numbers are given for both eastings and northings. The numbers for these lines begin at 00 and end at 99. But six figures can be used to provide more accuracy.