OS 50K Symbols - Heights and Rock Features

Creative Commons Licence [Some Rights Reserved]   Text © Copyright March 2007, David Hawgood; licensed for re-use under a Creative Commons Licence.
Images also under a similar Creative Commons Licence.


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 SymbolsExternal link 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 ScotsmanExternal link
NN7154 : Schiehallion by Callum Black 1:50,000 Modern Day Landranger(TM) Map © Crown Copyright

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!
SW4528 : Mount's Bay, West Cornwall by Frances Watts 1:50,000 Modern Day Landranger(TM) Map © Crown Copyright

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.
NG5423 : Descent to Bealach na Beiste by Gordon Hatton 1:50,000 Modern Day Landranger(TM) Map © Crown Copyright
As the ground becomes even steeper even the thicker 50m contour lines merge together as in NN1672 : Cloud Inversion - North Face of Ben Nevis
NN1672 : Cloud Inversion - North Face of Ben Nevis by David Crocker 1:50,000 Modern Day Landranger(TM) Map © Crown Copyright

SX8475 : Reclaimed clay spoil heap, Brocks Farm Contour lines are discontinuous in some pits and dunes.
SX8475 : Reclaimed clay spoil heap, Brocks Farm by Derek Harper 1:50,000 Modern Day Landranger(TM) Map © Crown Copyright
- 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.
NH5836 : Loch Ness. by Nevin Arrow 1:50,000 Modern Day Landranger(TM) Map © Crown Copyright
In Loch Oich, lines are at 10 metre intervals, deepest at 30m.
NH3302 : Loch Oich
NH3302 : Loch Oich by Richard Webb 1:50,000 Modern Day Landranger(TM) Map © Crown Copyright

Height


NN9231 : Botich
NN9231 : Botich by Lis Burke 1:50,000 Modern Day Landranger(TM) Map © Crown Copyright

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."
TQ1684 : Trig point on Horsenden Hill by David Hawgood 1:50,000 Modern Day Landranger(TM) Map © Crown Copyright

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 archiveExternal link gives heights of most benchmarks - enter the grid square reference to get a list.

Rock features

Outcrop

NG2352 : Outcrop on Beinn Mhic Uilleim
NG2352 : Outcrop on Beinn Mhic Uilleim by John Allan 1:50,000 Modern Day Landranger(TM) Map © Crown Copyright

Cliff

NM4337 : Basalt cliffs, Isle of Ulva
NM4337 : Basalt cliffs, Isle of Ulva by Gordon Mellor 1:50,000 Modern Day Landranger(TM) Map © Crown Copyright

Scree


NY1504 : The Screes of Illgill Head.
NY1504 : The Screes of Illgill Head. by Steve Partridge 1:50,000 Modern Day Landranger(TM) Map © Crown Copyright
KML
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