Spot Heights and Trig Points

Spot height on Knocknacloghoge

This is an example of how a spot height is shown on a map. The mountain used in this example is Knocknacloghoge in the Wicklow mountains and its spot height is 534m above sea level. Copyright Ordance Survey.

Spot height on Knocknacloghoge

Spot height on Knocknacloghoge

This is an example of how a spot height is shown on a map. The mountain used in this example is Knocknacloghoge in the Wicklow mountains and its spot height is 534m above sea level. Copyright Ordance Survey.

Enlarge image

On the top of hills you will see a dot and a number written beside it.

The dot will be inside a small enclosed contour line.

This map of Knocknacloghoge shows a dot with the number 534 beside it, inside a small enclosed contour line.

This is a Spot Height and it means that Knocknacloghoge is 534m above sea level and that this is the top of this particular hill or mountain.

Example of a Triangulation Point - Djouce Mountain, Co. Wicklow

The section of map shows a Triangulation point on the top of a mountain. Triangulation points (or 'trig points') are small concrete triangles, truncated at the top. They are used by cartologists (map makers). (c) Copyright Ordnance Survey Ireland

Example of a Triangulation Point - Djouce Mountain, Co. Wicklow

Example of a Triangulation Point - Djouce Mountain, Co. Wicklow

The section of map shows a Triangulation point on the top of a mountain. Triangulation points (or 'trig points') are small concrete triangles, truncated at the top. They are used by cartologists (map makers). (c) Copyright Ordnance Survey Ireland

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Trig points or Triangulation Pillars are another way of spotting the top of a mountain on a map.

The symbol for a trig point is a small triangle.

Look at Djouce Mountain on this section of map. Can you see the triangle? The number beside it shows the height above sea level.

Triangulation pillars are used by map makers. They are real concrete pillars that are placed at particular places which are usually the tops of hills or mountains.

Triangulation, Point, Djouce, Mountain, Wicklow

This image shows a triangulation point on the top of a mountain. Triangulation points (or 'trig points') are small concrete triangles, truncated at the top. They are used by cartologists (map makers).

Image appears courtesy of Simon Stewart of www.MountainViews.ie

Triangulation, Point, Djouce, Mountain, Wicklow
Image appears courtesy of Simon Stewart of www.MountainViews.ie

Triangulation, Point, Djouce, Mountain, Wicklow

This image shows a triangulation point on the top of a mountain. Triangulation points (or 'trig points') are small concrete triangles, truncated at the top. They are used by cartologists (map makers).

Image appears courtesy of Simon Stewart of www.MountainViews.ie

Enlarge image

Look at this photograph of a triangulation pillar. Can you can see that it is at a high point in the landsacape?

Even though it may be hard to see in this picture, triangulation pillars have four sides. They are usually about 1 metre high and flat on the top.

If you are hill walking and see one, you can check the map and confirm what part of the landscape you have reached.