The last blog in this series dealt with grid references as an effective and safe way of  navigating from point to point. It stressed the importance of being able to read a map, identify potential hazards, and plot a safe route accordingly.  This blog looks at features as an essential part of  route planning.

The first part –Identifying Features looks at how features are represented on a map. The second part – Navigating using features –looks at we use features to plan a route and navigate “on the run.”




The blog will look at features in and around Loch a’ Duin, an area that is used regularly by members of Tralee Mountaineering Club (TMC) to practice navigation skills.



A feature is a distinctive detail in a landscape that can be easily identified on a map and given a grid reference (plotted). Some features are easy to spot on the the Ordnance Survey Ireland (OSI ) 1:50,000 maps because they are represented by a combination of symbols and colours –  a trail (—), a wall (––), a river  (––), elevated ground or spot height (•73),  a summit (brown circle, spot height, and name where relevant), Special features like archaeological sites () are also marked. Some maps (Harvey) have symbols for crags, cliffs, boulders, scree, and other features.

The full list of symbols is given at the bottom of the 1:50,000 map and it is important to be familiar with the key features that are used for navigation in the mountain – tracks and trails, walls, rivers/streams, lakes, spot heights, and summits and so on.





This is the easy bit.

Most features in the mountains are described by contour lines on a map. Contour lines are the continuous lines that represent changes in height in the landscape. Being able to read and interpret contour lines is an essential part of safe navigation.



Contours-and-relief (1)
Source: OS Great Britain
Topographic Maps
Source: Topographic Maps YouTube


The section of map above shows contours as they appear on OSI Map 70. The diagram below it shows how contours represent changes in the height and profile of mountains. The third image is a useful representation of the relation between contours and the landscape. Map reading involves using changes in height and profile on the map to identify features in the mountains and vice versa.

This video by Steve Blackhall of the Ordnance Survey office in Great Britain is a good introduction to the contours, just be aware that the maps used in the video are British maps.







Navigating with contours involves thinking about the relation between contours and characteristic features in mountain landscapes. There are two aspects to this, knowing where you are and  avoiding hazards. The first has to do with being able to read a map  and the second has to do with planning and following a safe route (navigating).

Lets look at the first part –  using contours to identify features. To begin, how do you know whether you are

  • at sea level or on top of a mountain?
  • on level ground or a steep slope?
  • on the top of a hill or in the bottom of a hollow?
  • in a valley or on a spur?

The answers are fairly obvious: Just look around you.  What if

  1.  you are planning a recce and need to plot a route through unfamiliar terrain?
  2. you are in the mountains and the weather has changed, leaving you with little or no visibility?

Take the following scenario. You are heading into to Loch An Duin from Kilmore Cross (Q52294 08919), intending to climb to An Starraicín (Q52769 06407) at a height of 456 metres (see map below). Visibility is less than 20m and you have to navigate by map. You have reached the edge of a lake but the map shows two lakes, one on either side of  An Starraicín.


How do you know whether you have reached Loch an Dúin or Loch Chom Calláin?


Loch A Duin Contours


Loch an Dúin is approached along ground that lies between the the 100m and 120m contours, rising 20 metres over a distance of one kilometre approx. The contour formed by the edge of the lake is given as 116 metres; the height of every lake is indicated by the blue coloured number on the “surface” of the lake. To reach the lake you will climb 1m in height for every 50m in horizontal distance travelled,  a gradient of 1:50.

Loch Chom Calláin is approached along ground that rises from 100 metres to 230 metres over a distance of 1.3 kilometres approx. The contour formed by the edge of the lake is given as 231 metres. The key feature here is middle section of the route. The contours between 130 metres and 230 metres are closer and more or less evenly spaced over a distance of 600m approximately. This means that you will be climbing 1 metre in height for every 6 metres in distance travelled, a gradient of 1:6. This is a very different profile to the approach to Loch An Duin.


The question now is this:

Did you approach the lake by travelling along relatively flat ground or by climbing a moderately steep slope?


This scenario demonstrates how you can use information provided by contours to identify features and confirm your location. This is a fundamental part of navigation. Certain features have characteristic contour profiles that make them easy to identify,   incorporate into route planning, or use when navigating “on the run.”


Here are some examples:





Here are some standard descriptions of each of the features shown above. All the features are on routes used regularly by members of Tralee Mountaineering Club (TMC). 


Summit / Peak

This is the top of the mountain. It is a point on a surface that is higher in elevation than all points immediately adjacent to it. It is usually marked with a brown circle, a spot height, and sometimes, a name – not all spot heights are summits and not all summits have names, Unnamed summits are usually referred to by the number (elevation) given as the spot height.


a continuous elevated crest running for some distance between summits. The sides of the ridge drop away from a narrow top.


Ground that runs down from a hill to lower ground. A spur is an erosional feature that usually forms the side of a valley. Spurs provide access to and escape from the high ground for mountaineers.

An aréte is a narrow rocky spur which separates two valleys. It is typically formed when two glaciers erode parallel U-shaped valleys.


A vertical, or nearly vertical, rock exposure. Cliffs are a real hazard but can be very useful as a “handrail,” a feature that you can follow, at a safe distance from the edge of course.


The lowest point of a ridge or saddle between two peaks, typically providing a pass from one side of a mountain range to another.


This is the side of the mountain, running from the summit to the foot. Slopes can be convex or concave.


A convex slope is rounded like the outside of an upturned bowl, i.e. it goes from less steep at the top to more steep at the bottom; the space between contours gets narrower as the elevation reduces.

A concave slope is rounded inward like the inside of a bowl, i.e. it goes from more steep at the top to less steep at the bottom; the space between contours gets wider as as the elevation reduces.


a small valley like formation formed by parallel spurs. The low ground between the spurs is sometimes called a draw and is usually associated with drainage or a rivers/stream.


gully is a long narrow valley with steep sides.




There are two types of features that can be used to navigate in the mountains. The first type is marked on the map using a combination of symbols, colours, and numbers and includes tracks/trails, rivers/streams, spot heights etc. The second type consist of formations that are characteristic to mountain landscapes and include summits, ridges, spurs, cols and so on. These features are described by changes in height and profile (shape) that are represented on the map by contour lines.




















Catherine McMullin, Dáithí Ó Conaill, and Monica Dillane of TMC investigating a megalithic tomb in Loch a’Duin.


Q 52763 08134


The above photo shows members of Tralee Mountaineering Club (TMC) examining a megalithic tomb in Loch a’Duin on the Dingle Peninsula. The tomb was placed in the valley using an ancient navigational system that was, apparently, centred on the Spring Equinox.

It is located on a small plateau east of An Scoraid river, about 900 metres southeast of the Kilmore junction on the Conor Pass road. The location is marked by a red dot on the 1:50,000 Ordnance Survey map; red dots signify the location of archaeological features in the landscape.




There is a more precise way of describing the location of the tomb. View Ranger gives its position as Q 52763 08134. This is called a grid reference, which is  an alpha-numerical set of geographic co-ordinates that is used to locate a feature on a map. Grid references are the basic unit of a navigational system that divides the country into twenty 100 X 100 kilometre zones. This is called the National Grid

Loch a’Duin is located in Q, one of two squares in the National Grid that cover the Southwest. This is the first element of every grid reference. It is followed by two set of numbers. The first is called the Easting (52763). The second is called the Northing (08134). These allow the navigator to zoom in on each zone, pinpoint the location of a feature on the map, and navigate towards it with confidence.




UTM and National Grid


This diagram shows the national grids of Ireland and Great Britain superimposed on a global grid, which is known as the Universal Transverse Mercator or UTM for short. It is named after Gerardus Mercator, a Flemish map maker who invented a system of world wide navigation in 1569.   The UTM was adapted to provide an agreed system of  geographical co-ordinates that could be used in global positioning systems ( GPS) like View Ranger.

The Ordnance Survey offices of Ireland and Northern Ireland adopted a modified version of the UTM in 2001. This was done to increase the accuracy of GPS measurements by minimising distortions in mapping across the island as a whole.  This is called the Irish Transverse Mercator (ITM) or, simply, the Irish Grid

The Irish Grid provides the organisational and geographical basis for navigation in Ireland but mountaineers usually use 1:50,000 maps. The ground covered by these maps is not the same as the area in each zone of the grid; each zone contains more than one map and many maps extend beyond the boundaries of individual zones.


Grid100km & Q
The Irish Grid (left) and a section of the grid superimposed on the corresponding 1:50,000 maps issued by Ordnance Survey Ireland (right).


Loch A’duin is positioned on Map 70 in zone Q of the national grid. Iveragh is located in zone V, the dividing line running along the southern shore of the Dingle Peninsula. Grid references for Iveragh – maps 78 and 83 – begin with the letter V. The zone is clearly identified on each map and the boundary between zones is clearly shown.







Each map in the 1:50,000 series uses a grid made up of 30 by 40 squares measuring 2cm and representing one kilometer on the ground. Each square is defined by a vertical and horizontal blue line. The vertical lines are called Eastings and the horizontal lines are called Northings.

Eastings measure distance from west to east. The line dividing East and West is called the prime meridian.  This was  agreed in 1884 as the line of longitude running through the Greenwich Observatory, near London.  Anyone who has visited the Observatory will recall a metal strip in the ground that marks 0º Longitude; the line dividing East and West and the first of the Eastings. The prime meridian used in GPS is approximately 102 metres East of this line. This will read as 0º on satellite based systems.


An aerial view of the Greenwich Observatory. The dotted white line represents 0º Longitude and the solid white line represents the line that divides East and West in modern global positioning systems. Source Why the Greenwich meridian moved.


Northings measure travel northwards from the equator.


Every Easting and Northing on a 1;50,000 map has a value between 00 and 99. On Map 70 the Eastings run from 20 to 60 while the Northings run from 88 to 99 and 00 to 18. Grid references contain two sets of numbers (co-ordinates) that define the position of a feature on a map in relation to Eastings and Northings, the Easting are always given first.

Q 52763  08134 is given as the grid reference for the tomb in Loch a’Duin.  52 refers to the Easting and 08 refers to the Northing.  These define a one kilometre square, which is read from the right (East) of the Easting and above (North) of the Northing. The point where these lines intersect –the bottom, left-hand corner – is called the origin and all travel eastwards and northwards within the square is measured from this point.


Easting Northing
The square formed by Easting 52 and Northing 08. Q 52000  08000 is the grid reference for the  origin, the point where the two lines intersect..


There is a problem with a grid reference that merely identifies a square on the map. It presents you with a square kilometre of ground to search for a feature that may only be three or four metres in size. The solution is simple. Each square is divided into a grid made up of 100m units. These are numbered 0-9 and are represented by the third number in the Easting and Northing component of a grid reference –  Q 52763  08134. This grid reference puts the position of the tomb in a 100m square that is 700m east of  line 52 and 100 metres north of line 08 on the map.


Grid 2&4


This still leaves us with a large area of featureless terrain to search but the last two digits of grid reference Q52763  08134 tell us that we have to walk 63m eastwards and 34m northwards from the origin of this square to locate the tomb. This coincides with the red dot that marks the location of an archaeological feature that is identified as a Tuama Meigiliteach.



Grid references are an essential part of your navigational skillset. They enable you to locate your position on a map, pinpoint features in the landscape, and navigate safely from feature to feature.



Grid 4


Use this system to generate grid references for the following features:

  1. The Gallán (Standing Stone) north of the tomb.
  2. The point at the edge of the forestry where a stream enters An Scoraid.
  3. Spot height 73.
  4. The start of the track leading into Loch a’Duin, from the Conor Pass road.
  5. The point where the track crosses the 100m contour.
  6. The point where the track meets An Scoraid.
  7. The point where An Scoraid crosses the 100m contour.

Handy hint:

You can use the 1:50,000 scale an your compass (Silva Expedition) to quickly and accurately establish a grid reference. Here’s how:


Romer IMG_8481

Q 52763 08134

Q (NATIONAL GRID) 52 (EASTING) 7.63 (100M GRID)  08 (NORTHING) 1.34 (100M GRID)


Here is another type of navigational problem.

There is another  way of navigating to the location of the tomb. Open View Ranger, place the red dot marking the position of the tomb at the centre of the crosshairs and mark with a Point of Interest (POI). Then activate the Navigate To function. View ranger will present you with an onscreen,  point-to-point route to your objective and will guide you along it in real time. Simple!

Here is the problem.

An Scoraid river lies between the track into the valley and the tomb. To reach the tomb by this route you will have to cross the river. River crossings are one of the most dangerous aspects of mountaineering.

Find the spot where the track is closest to the tomb and read the course of the river in relation to the contour lines. The river is flowing through a fairly narrow  re-entrant. Would you consider crossing the river at this point?

Have a look at the flat area north of this, where the river drops from the 100m contour to the 90m contour over a distance of approximately 200m. Does this look like a better option? Remember a 10m drop is equivalent to the combined height of 5 very tall people.

The river is a very dangerous feature between you and your objective, the tomb. You need to navigate to a safe river crossing first, then from the river to the tomb. If you can’t identify a potentially safe crossing, don’t go to the tomb by this route.

The point is this; grid references allow you to pinpoint the position of a feature but you still need to (1) understand the nature of the terrain in which that feature is located and (2) be capable of assessing the risks and the opportunities presented by it. That is where skilled map reading contributes to safe navigation.


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