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Vegetation: very difficult to run, impassable 410

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This page contains content from ISOM2000   This page contains content from Ashby Mapping      revision 05/00


410 Vegetation: very difficult to run, impassable

An area of dense vegetation (trees or undergrowth) which is barely passable. Running reduced to ca. 0 - 20% of normal speed.

Colour: green 100%.

Minimum line width 0.25mm

ISOM 1990 Definition

As ISOM 2000 but runnability bad extended from 0-10% to 0-20%.

OCAD Methods

Defined as area symbol 410.0, and can be drawn with any drawing tool.

Care is needed at joins, overlap only where it is safe (usually if it is the same colour and always if it is the same symbol). If you need to share a common boundary with another symbol, draw along the edge with the control key to follow it exactly.

Drawing Considerations

The runnability depends on the nature of the forest (density of trees/brushwood and undergrowth- bracken, brambles, nettles, etc.) but does not take account of marshes, stony ground etc. which are shown by separate symbols. There is a runnability topic.

See minimum dimensions but specifically -

- Smallest area enclosed by a dotted line: 1.5mm (diameter) with 5 dots.

- Smallest area of colour green full colour: 0.5mm˛.

Hedges and linear thickets shown with this symbol do not look right with the crossing point symbol, just use a gap. Make the gap at least twice the thickness of the line for clarity.

Permissible Combination of Screens

The ISOM lays down the permissible combination of screens.

Vegetation (very difficult to run) is allowed with broken ground, stony ground, marsh, and indistinct marsh,

but not with uncrossable marsh, open land, open land with scattered trees, rough open land, rough open land with scattered trees, forest: slow running, undergrowth: slow running, forest: difficult to run, or undergrowth: difficult to run

Pictorial Descriptions

- BOF Rules, Appendix One

Thicket: an area of forest where the tree cover or undergrowth is so dense that it is difficult to pass.

Felled area: an area of felled or fallen trees.

Hedge: a line of trees or bushes marking a boundary.

Linear thicket:a line of trees or bushes that is difficult to cross.

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International Specification for Orienteering Maps produced by the International Orienteering Federation
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Produced for the Ashby Mapping internet site on 20 November 1997 and 1 December 1999  ©1997-2000 Ashby Mapping
Revised 28 December 1999, 23 March 2000