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#NationalMapReadingWeek : The Twitter Quiz – Answers

20 October 2016

It’s one thing to sit at the kitchen table one weekday evening with the map spread out in front of you as you delight in planning your next Sunday walk. You’ve plenty of light to see-by. The minor draught coming through the kitchen door is nothing compared to the 50km winds you might experience walking along a ridge. And assuming your roof is in good order you are likely to be warm and dry.

It’s quite another when you are actually out there. The cloud base has dropped. An unexpected front has passed over, the temperature has fallen, humidity risen and it’s started to rain. Your companions want to cut the walk short, and you need to look at the map and find a safe “escape” route quickly.

What makes this map easy to read..?

To help you discover how a map is made so that you can work efficiently in those conditions, I asked five other questions, each one focusing on one bit of map detail. Looking at those and the answers should help us  to discover why the map is drawn this way. And what makes one map more suitable than another when you are out on the mountain. So read on…

Question 1:

The map is flat, but the hills are not. You may already know that we use contour lines to draw the shape of the mountain. Each contour line connects together the sides of the mountain that are the same height above sea-level. Each contour represents a different height -that height is usually written on the contour or it’s neighbours.  Even from the map extract above we can see how these lines can be used to draw a three-dimensional picture of the mountain. In this case there is a rough triangle of three peaks, they are: Slieve MeelMor (left one), Slieve Bernagh (right one, upper in the picture) and Slieve Meelbeg (lower right in the picture). You can see how the height in metres, written on the contours, gets higher the closer the contours get to the summit and how they show the shape of the mountain.

So why 15 metres and not 10m or 20m? This is about giving you the most accurate picture of the mountain as possible. But without having places where the mountain sides are so steep, that the contours become squashed together on the map and become of no use. Or the lines are printed so finely, they are impossible to interpret when you are struggling in the wind and the rain. So looking at the map above, in the case of the Bearnagh Slabs (in the upper middle of the picture) contour lines placed every 10 metres would simply be too close together for them to be easily read on the mountainside.  25 or even 20 metres would work fine, but then we could be getting less detail about the shape of the mountain, as the map-maker would be using less contour lines to draw it..

So generally, for us walkers in Britain and Ireland, drawing a map with contour lines representing heights every 15 metres makes it possible to for the map maker to use bold lines and  for us to see the shape and slope of the mountain.  Getting as much information as possible, without making it too difficult to read when you are on the mountain side.


Question 2:

We already know the contours are telling us the shape of the mountain. That the closer they are together, then the steeper the slope. And that their frequency is about giving us as much information as possible without cluttering the picture.

Now this clever device of changing the colour of the contour, still keeps the picture clear, but gives us more information about the mountain under our feet. When the brown contour lines turn to grey we know the ground will be predominantly rocky, possibly hidden under grass tussocks, moss or algae, possibly bare, we will have to look. But the map has told us what to expect. And experience tells us this may present a hazard if or when we try to cross it.

So, if we are leading a group, or by ourselves, then maybe taking that NE running spur to that inviting track in the valley below is not the best route off Slieve Commedagh in a storm.


Question 3:

Map makers can use colour or patterns to indicate important information about the landscape. Research shows that both seem to work as effectively, and this is an example of the combination of the two. Refraining from using a block background colour makes the other information (such as spot heights and names) easier to read. And using a pattern in colour prevents the pattern from confusing the background information, such as the contour lines.

wp_20161011_021The map key tells me this is an area of “hags”. And this picture shows what this spot looks like. Those mounds (rising to 3 metres in parts) are the hags. Groughs are the channels between them. All this at its most hazardous time – in cloud and fog. The area of reddish-brown bog cotton is likely to be seasonally wet but the sheep prints in the foreground show you the peat is soft, but not deep. The area to the right is quite dry and easily navigable – but it may be forcing you to walk in the wrong direction. The juniper shrubs on the skyline make useful navigational aids


Question 4:

Regular map readers will understand the idea of the Map Grid, a way of dividing the country up into 1km squares and numbering them. Counting first from left to right and then from bottom to top will let you identify a particular 1km square. We call that a grid reference, and it means you can identify any spot in the country, usually within a 10 metre square. (I’ll be updating my published “how to” on using grid references soon, and putting it here on Best Walks).

On many maps the grid reference number can be found at the very edge of the map, and frequently to find out where you are you need to unfold the map and trace your finger to the edge to read off the number. And you have to do this twice. (left/right and up/down).

But on this map the last two digits for the grid reference are printed directly on the East/West and North/South grid lines, so that when the map is open as in the example in this picture, you’ve always got the most important part of the grid reference available “at a glance”.

And if you are a GPS user (one without maps) or maybe using a GPS smart phone app, that just gives you the grid reference and does not display a map, it becomes very easy to read the reference from your device and place yourself accurately using the grid on the map even as you are walking.


Question 5:

It’s all about clutter. This is not a map for school room geography or courthouse debates. It’s about helping you across the landscape on foot as efficiently and as safely as possible. Map makers have to decide what information is relevant to the user of the map. Too little information and the map might be more of a danger than a help. But display too much information and it becomes difficult to discern what’s important. And at critical times it can act as a distraction from reading and interpreting the map.  Experiments have even shown that lines that you have to cross, can affect your judgement on distance, quite dramatically. So maps like this focus on what’s important for you on the mountain.


And again : What makes this map easy to read..?

It’s the overall approach. The map maker has concentrated solely on the needs of the walker.

They’ve thought about:

  •  How many lines should go on the map and what they should be used to represent. Making sure there are enough to give you adequate information, but not so many as to clutter your view. The same approach has been taken with text and reducing the naming of features in the landscape. It’s all about reducing clutter.
  • There has been a careful consideration of the use of colour. Block colours identify lowland areas, forestry and water. But the more hazardous mountainous areas are left white, to allow emphatic and bold use of contours. And coloured patterns too, used to illustrate some quality of the landscape underfoot. Whilst the technical opportunity to change the colour of a contour is used to show a change in conditions.
  •  Even the best manner of folding the map and using the folded map has been considered. You can read more about that in the review of this map here. But especially important, is the ability to see the Eastings and Northings figures of the 1km squares of the Irish or British map grid. Great for those who thumb their way along the map as they walk, and for when the wind makes it impossible to open up your map and take readings from the edges.


What map did I use?

These images are taken from the Harvey Maps SUPERWALKER map of the MOURNE MOUNTAINS. It is 1:25000 scale, GPS compatible and waterproof. These poor quality smartphone camera images (taken by DM) are used with their courteous permission.  You can read the full review here.
All images remain the copyright of Harvey Maps Ltd.

I’m currently using the 1:3000 scale map from the same Harvey Maps SUPERWALKER series for the WICKLOW MOUNTAINS and I will publish the review here on Best Walks

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