See Also...407 408 ISOM Index Vegetation index previous next
revision 05/00
409 Undergrowth: difficult to run
An area of dense undergrowth but otherwise good visibility (brambles, heather, low bushes, and including cut branches) which reduces running to ca. 20 - 60% of normal speed. This symbol may not be combined with 406 or 408.
Colour: green 28.6% (23.8 lines/cm).
Line size 0.12, line spacing 0.12mm (0.30mm line to line)
This symbol is oriented to north.
As ISOM 2000 runnability band changed from 10-50% to 20-60%. Drawing specification completely altered.
It was: -
Colour: green 33% (27 lines/cm).
Line size 0.125, line spacing 0.25mm (0.375mm line to line)
Defined as area symbol 409.0, 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.
This is a rotatable symbol, the pattern of the fill can be rotated with the direction tool and will rotate with the map if the “include symbols” box is checked when the map is turned. This is not the same as using the rotation tool which turns the whole object, but not the fill pattern.
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: 1.5 mm (diameter) with 5 dots.
- Smallest area of colour green dot screen: 1.0 mm˛.
The ISOM lays down the permissible combination of screens.
Undergrowth (difficult to run) is allowed with broken ground, stony ground, marsh, indistinct marsh, rough open land, and rough open land with scattered trees,
but not with uncrossable marsh, open land, open land with scattered trees, forest: slow running, undergrowth: slow running, forest: difficult to run, or vegetation: very difficult to run.
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.
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