OS 50K Symbols - Heights and Rock Features

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This is one of a series of articles which give photographs of features on the ground which have standard symbols on Ordnance Survey 1:50,000 maps, with map extracts showing the symbols. On the maps a blue circle is on or near the symbol. Use the mouse to move the pointer over the blue circle on a map to hide it. Click on a thumbnail to see a page with a larger photo, other photo details, and a larger section of the 1:50,000 Ordnance Survey map. The article Ordnance Survey Map Symbols gives an introduction, and links to others in the set of articles.

As heights and contours are not visible on the ground, the examples show areas where the symbols appear on the map.

Heights

Contour and contour height

NN7154 : Schiehallion Schiehallion where contour lines were invented see Heritage Scotsman
[smallmap NN712542]

SW4528 : Mount's Bay, West Cornwall Above Newlyn as heights are shown from mean sea level in Newlyn Harbour. The figures are upside down in this example - the height in the circle is 90 metres not 06!
[smallmap SW457286]

In steep terrain contour lines may become too crowded to be shown on the map. Where this happens one or more of the thinner lines at 10m intervals are omitted, and those remaining are showing the form of the ground rather than being strictly contour lines. The example below NG5423 : Descent to Bealach na Beiste shows a line with an end, as the ground becomes steeper.
[smallmap NG542234]
As the ground becomes even steeper even the thicker 50m contour lines merge together as in NN1672 : Cloud Inversion - North Face of Ben Nevis
[smallmap NN163722]

SX8475 : Reclaimed clay spoil heap, Brocks Farm Contour lines are discontinuous in some pits and dunes.
[smallmap SX 8424 7589]
- also see TF8645 : Sand bowl in Burnham Overy Dunes

Depth of inland waters

Depths are shown with blue contour lines. In the first example, and in most of Loch Ness, lines are at 50 metre intervals, deepest at 200m. These underwater contour lines and depths are not shown separately on the OS key to symbols.
NH5836 : Loch Ness.
[smallmap NH 5859 3641]
In Loch Oich, lines are at 10 metre intervals, deepest at 30m.
NH3302 : Loch Oich
[smallmap NH 3331 0233]

Height

NN9231 : Botich
[smallmap NN925312]

TQ1684 : Trig point on Horsenden Hill The map for this example shows two heights. The key on recent OS Landranger maps says: "Where two heights are shown, the first height is to the base of the triangulation pillar and the second (in brackets) to the highest natural point of the hill."
[smallmap TQ 1610 8430]

Note that there is rarely a spot height shown at a benchmark, except those on trig pillars where the height shown is that at the base of the pillar. Other benchmarks are not shown on 1:50,000 maps. OS benchmarks and trig archive gives heights of most benchmarks - enter the grid square reference to get a list.

Rock features

Outcrop

NG2352 : Outcrop on Beinn Mhic Uilleim
[smallmap NG 2342 5262]

Cliff

NM4337 : Basalt cliffs, Isle of Ulva
[smallmap NM434379]

Scree

NY1504 : The Screes of Illgill Head.
[smallmap NY 1525 0455]

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