Grid references in Great Britian using the national grid

Britain’s national grid system

Britain’s national grid system is unique as most countries use the latitude and Longitude system of establishing position.

The National grid system is very easy and very accurate to use.

Learn how to use it, Understand the 100 km. main grid squares, the sub division into 1 Km. grid squares and accurate use of six figure grid references.

to see how this is done, scroll down

In the example below is a section of the detail of the 1:50,000
Landranger map. It is from Landranger map number 41 of Ben Nevis

the blue squares are the grid lines that form part of the national grid.

these squares are one square kilometre in size
and are used to give the actual grid reference

Image produced from the Ordnance Survey get-a-map service.
Image reproduced with kind permission of Ordnance Survey

www.nigelspencer.co.uk

to get a grid reference
you always give the number across the bottom first (west to east)
the second figure is the upwards number (south to north)

Look at the map below and find the summit of Ben Nevis
(a blue triangulation point) at 1344 meters high

a four figure grid reference will give the actual square the feature is in
therefore the four figure reference on the summit of Ben Nevis is
16 71
in reality this is a large area so to get a more accurate reference we sub divide it further to a six figure reference

this six figure reference is gained from using "imaginary"
grid line further dividing the grid square into 10 both from
"west to east" and then from "south to north"
therefore the six figure reference for the summit of Ben Nevis is
166 713

Image produced from the Ordnance Survey get-a-map service.
Image reproduced with kind permission of Ordnance Survey

www.nigelspencer.co.uk

Now that we have the six figure grid reference for the summit of Ben Nevis 166 713

We have to find a way to make it unique to the summit as the grid keeps repeating itself every 100 kilometres.

We can not use the grid reference and the number of a map e.g. 41 / 166-713

This is especially important if using a GPS
as GPS technology uses the 100 Kilometre squares

using
the British National Grid
100 Kilometre squares

Britain is divided up into 100 KM squares

these squares are given two identifying letters

to give an accurate grid reference

give the grid square
followed by the numerical grid number

an example of this is for the location of Ben Nevis summit
we would use the reference

MN 166713

(this represent a location of the 100 Km square & then the actual 6 figure reference)

Therefore for an "accurate and correct" location on Ben Nevis summit

we would use the reference

MN 166 713

remember this reference would be for a 100 meter square (a big area on Ben Nevis)

approaching the summit
of Ben Nevis