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revision
05/00
101 Contour
A line joining points of equal height. The standard vertical interval between contours is 5 metres. The smallest bend in a contour is 0.25mm from centre to centre of the lines.
A line joining points of equal height. The standard vertical interval between contours is 5 metres. (Line width 0.125mm)
Colour: brown.
Line width 0.14mm
Defined as line symbol 101.0. Can be drawn with any tool but bézier mode is preferable.
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Check the general comments on land forms note especially the following:-
Orienteering terrain is normally best represented with a 5m contour interval. An interval of 2.5m may be necessary in certain types of terrain. It is not permissible to use different intervals on the same map.
It is permissible to alter the height of a contour slightly if this will improve the representation of a feature. This deviation should not normally exceed 25% of the contour interval and attention must be paid to neighbouring features.
With careful editing some form lines and knoll / depression groups can be generalised with contours.
1) Contours will break at roads due to the street infill colour being higher in the colour table than brown. Brown can be moved up, but beware that it will then overprint more colours, including blue.
2) Drawing over a template only allows the visible section of the contour to be digitised. But when a digitising tablet is used, the extent of the contour can be extended to the amount that will fit on the tablet.
3) The joining tool will only align the ends of contours; it will not combine them into one object. To do this you will need a further program such as Conjoin from Don Scarrott or Joinline from Martin Green.
4) Freehand contours do not look as professional as bézier drawn lines. They are also harder to edit.
5) Auto trace, investigate autotracing of the brown drawing for a previously surveyed orienteering map. More details in the OCAD Help File.
6) The default contour is defined with rounded line ends. This is fine for contours, but is unsuitable for other thin brown lines such as 104 Slope lines.
7 Breaking of contours
If any line has been drawn in parts, there may be more than one object that appears to be continuous. Check by zooming out and changing the line to a thick purple line symbol (IOF 707) to see it's extent.
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