Map Reading – Read our articles on how to take a grid reference, and other navigation tips in TRAIL magazine. Why not join us on a foundation or intermediate map and compass course?
The most common mistakes are –
1 Getting the Eastings and Northings the wrong way around
2 Confusion when the first two digits end in a zero, for example 30 1 is recited as 31 and a digit is missed.
Map reading skills – Grid references are often used to uniquely identify a point for perhaps when route planning, entering a waypoint into a satnav, or just describing somewhere on a map. For example, if you say, ‘meet you at Blea Tarn’ in the Lake District, expect someone to ask, ‘which one’?
The time you really need to get it right though is if you have to call out Mountain Rescue and describe your location. If you do an emergency call from a mobile phone on high ground, you may get through to a Police force in a different county from where you are, and they do not know the area you are in at all. The initial call handler may be used to urban incidents working only with postcodes and addresses rather than grid references, so the more specific information you can provide the better.
So here is an easy way to always get Grid references right:
Map Reading skills – Grid references Step 1. Identify the map you are on. The most common hillwalking maps, OS 1:25000, have a unique identifier, two letters in light blue, for the map you are on. Always quote this at the start of every grid reference as it makes your grid reference unique.
On this picture it is NY. So, all grid references start NY on this area of the map. (Some people think this is a post code it isn’t. It denotes a 100km grid square for this area of this map.)
Map Reading skills – Grid references Step 2. Remember along the corridor and up the stairs.
Some people do not like this saying but it can help you remember which way to start. Go from the left hand side of the map to the right along ‘the corridor’ to find the blue grid line that is nearest and on the left of the feature you want to identify.
(The term is called the Easting.)
So, we started the left and look at the nearest grid line to the left of our feature.
In this case the pond near Brownrigg Moss is 29 something.
Now we go ‘up the stairs’ from the bottom of the map to the top.
(This term is called the Northing).
For the pond near Brownrigg on this map, the nearest grid line underneath our feature is 10, so our grid ref now ends 10 something.
So, NY 29 10 is the 4-figure grid ref of the pond. A grid square always quotes the bottom left hand corner of the square that your feature is in.
But that 4-figure grid ref is only to the nearest 1 km square, not much use to pinpoint a feature. We can be much more accurate with a 6-figure grid ref and get to within a square 100m by 100m. This is still bigger than Wembley’s pitch, but better than 1km.
Map Reading skills – Grid references Step 3. To get to a 6-figure grid reference, now split the 1km square up into 10ths
The square we identified is the NY 29 10 square, imagine we now split this 1km square up further into 10ths along the corridor and 10ths up the stairs.
You can do this visually and mentally just by looking at it, or with the roamer scale on your compass, or with a special grid reference tool which splits the grid square into 10ths for you.
Top Tip – If using a grid ref tool or roamer, you have to remember to use either the 1:25000 square or 1:50000 square depending on which OS Map you are using. In our examples, we are using a 1:25000 OS map.
Here is our NY 29 10 square and now we imagine the square split into 10ths along the corridor and 10ths up the stairs. (see pic)
We have drawn our ‘imaginary lines’ over our NY 29 10 square for you on in this example in thick blue with red numbers, but you can do it mentally or with a roamer or grid ref tool.
Along the corridor and up the stairs we go – Half way ‘along the corridor’ or across the 29 square in our example, is obviously 5/10ths across, and Brownrigg Moss pond is about 7/10ths the way across or 7/10ths ‘along the corridor’.
So our Grid Ref is now NY 297…
Now going ‘up the stairs’, we can see that the pond is roughly between 4/10ths and 5/10ths the way up the 10 square in our example, so as we take the nearest below, it is 4/10ths up the 10 square. The grid ref ends then …104.
Our Grid Ref is now NY 297104.
Therefore, the full six-figure grid reference for the pond at Brownrigg Moss is NY 297 104.
(But what happens if the feature happens to be bang on the blue grid line? Don’t forget to add a zero. So, if your feature was actually on the NY 29 easting grid line, in a 6-figure grid ref that would be NY 290 (zero tenths of the way across the 29 square).
Why not try one now for yourself?
Look underneath the big NY letters on the picture. To the West of Calf Crag there is a Cairn near the 537m spot height.
You have come across a walker with a broken leg at that location. What is the six-figure grid ref of the Cairn that you going to give to Mountain Rescue?
(Answer- NY 301 104).
Top Tip. Always tell Mountain Rescue a Grid Reference and a description just in case in a panic you or the 999 call handler transposes a number the wrong way around. That way MR can verify it. So, say ‘the casualty and I are at Grid Ref NY 301 104, which is the Cairn near a 537m spot height, just West of Calf Crag on Grasmere Common, in the Lake District’.
Hopefully now you will remember your map reading skills and the right way around to do grid refs, even in a panic – along the corridor and up the stairs!
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