Grid References - how they work and how to use them.
I mentioned at the start of this article the six-figure numbers that are at the start
of my walks. These are Grid References. Every place on a map has one, and, what's
more, it's unique. Modern electronic navigation devices, which rely on communications
satellites in geosynchronous orbit, can plot your location to the nearest metre square
of ground - but what use is knowing that your Grid Reference ('Grid Ref') is 8532643434
if you can't find it on the map! For practical purposes, most Grid Refs are given
as six-figure numbers. This will place you in an area 100 metres square - accurate
enough for our purposes.
The whole of the British Isles is divided into squares 100,000 metres on a side (100
kilometres). Each of these large squares is given a reference comprising a letter
pair - ST for example. Landranger and Pathfinder maps are divided further into areas
1,000 metres (1 kilometre) on a side. To identify any one of these squares, two things
are needed.
The first is the letters (ST). The second is a four-figure reference, say 8534.
(These aren't real references, they're just examples, but the principle is exactly
the same on any map.) So what do they mean? Well, the extremely large square that
encompasses the whole country has as its starting point for reference its bottom
left-hand corner, or its South-West extremity.
The six-figure Grid Ref for this point would read 000000. It follows that if you
could stand on this point, the only way you could move within the giant square is
East or North. Map references start with Eastings (moving Eastwards from the start
point), then Northings (moving North from the base line). An easy way to remember
this is that 'E' comes before 'N' in the alphabet.
As you begin to move East from the corner, every 100 kilometres you will encounter
an Easting line, which runs South - North up the map. Similarly, Northings run West
- East across the map. If this sounds all horribly confusing, have a look at Fig.
1 which (hopefully!) will make things clear. I know it's animated but I thought I'd
try to kill two birds with one stone here.
A handy tool for grid reference finding is produced by Where-Wolf.com. In their words,
"Where-Wolf.com Grid Reference Finder. The easy way to give a grid reference. Map
reading made easy!" I do hope so!
Notice that the reference 'ST' appears on the map and that the 'town' (the blue square)
has the number 2215. This means that as you travel East (to the right), the last
Easting line is, in this case, Number 22. Stop there! Next look for the last Northing
line before the town - 15, right? So you now know that the 'town' is to the East
of line 22 and to the North of line 15. Its Grid Ref. is therefore ST2215.
It always works this way - the Grid Ref. is always the square to the East and North
of the figures given. The second reference - ST248166 - refines the area that the
square indicates. How? Well, the larger square is subdivided into smaller squares,
ten on a side. It follows that if the large square is one kilometre square, the smaller
squares must be 100 metres square (1,000 divided by 10 = 100).
First count to the last major Eastings line - 24. Then count across until the last
'imaginary' fractional Easting before the red blob - (lets say its a hilltop) which
is not shown as a line on an OS map - is reached. That figure is 8, thus giving
an Easting of 248.
Now perform a similar operation with the Northings. Last major line = 16, then up
to the last line before the 'hilltop' = 6. This give a Grid Ref. of ST248166, the
square in question being to the East of '248' and the North of '166'. And that's
all there is to it! Try getting hold of a Pathfinder map and plotting Grid Refs for
points of your choice - honestly, you'll very soon get the hang of it!
Right - click on the link below and let’s see about how to choose and use a compass!
GET QUOTE