Lines - Giving Widths to Lines

The Width dimension in lines, normally W=, can be used to give a survey feature a width and there are two ways the width can be used.

If a feature is width scalable, such as a hedge, the line that is displayed will be scaled up such that the width of the line pattern is the same as the value in the dimension.  The attribute check button Width Scalable is used to signify whether a line feature of this type.  The attribute check button Offset Half Width will also be enabled and this allows you to survey the face of the feature and offset the displayed line by half the width.  For this type of line width, the width dimension can be changed at any point and the new value of the dimension will then be used until it is replaced.  You should note that the width of each line segment does not taper between two points.

If a feature is not width scalable, you can still apply a width dimension.  In this case, two lines will be displayed that are the value of the width dimension apart.  The centre line of these two lines is the surveyed feature.  The initial width should be assigned to either the first or last point on the feature.  Note that if the attribute check button P,O&W on First Only is ticked, n4ce will not look for the width on the last point of the feature. The initial width dimension will be used until another width dimension has been assigned to a point.

Width Scalable Feature	Offset Half Width Scalable Features	Feature with Width Applied

The first of the examples above is that of a width scalable feature.  The second is the same but with the feature being offset by half of the width.  The third is that of a simple line feature width a width applied thus using the surveyed line as the centre line of two parallel lines.  Note that the option to close the ends of the feature has been applied using the Close Ends on P&W check box.  The above examples assume a constant width.

If the width varies along the feature, the calculations used are once again dependent upon whether the POW Variable check button is checked.  If is not checked, the width will not vary along each segment whilst, if it is, the lines either side will “splay”.  If we take the examples for parallel lines with varying widths and assume that the surveyed line is the centre line between the two constructed lines, the same result would be produced for the same values of width.

If the line is not width-scalable and there is a need to display a centre-line between the two parallel lines, you can specify a default field called FCL containing a code prefix to use.  If this is defined, a centre-line will be generated using the line colour and style for that code prefix.