Hachuring Symbols

Hachuring is often used to indicate the presence of steep slopes.  The Hachuring option from the DTM Tools menu allows you to create symbols where hachuring is necessary.  In the past, hachuring has often taken the form of tadpoles.  When selected, the pop-up menu below will be displayed.  There are two types of hachuring which can be created.

Feature - This option allows you to generate hachuring to one side of a feature.  This is normally used at the edge of a model to give an indication that the model falls away steeply in that direction.  With this option, the lines making up the hachuring will have a constant length.  You will be asked to indicate the line feature and the side on which the hachuring is to be created.

Between - This option allows you to generate a hachuring between two features, for instance a top and a bottom of an embankment.  With this option, the lines making up the hachuring will have lengths which vary by length along of the embankment at any given point.  You will be asked to indicate the two features and should indicate the top feature first.

When hachuring is placed on a model slope, you would normally not wish to contour that slope as this could make the presentation confusing.  You can use the DTM group functionality to overcome this where there is an option to turn off contours for a group.  Grouping the DTM triangles under a single group and enabling this option will remove any confusion.

When either option is selected, the dialog box shown below will be displayed enabling you to define the hachuring parameters.

The Pen and Layer fields allow you to define colour of the hachuring and the layer on which it will be placed.  The Type field defines the type of hachuring that you wish to create and there are three options.

Lines - Simple, solid lines will be generated from the top string in the required direction.

Symbols - A two-point symbol will be used and stretched from the top string in the required direction.

Both - A combination of a symbol and a line will be generated from the top string in the required direction.

The Attributes group allows you to further define the generation of the hachuring.  The Top Offset and Bottom Offset fields define the offset of the hachuring lines from the top and bottom strings in millimetres.  Note that the latter of these offsets has no effect when hachuring from a single feature.  The Spacing field defines the spacing along the top feature at which hachuring lines are generated and should be defined in millimetres.

The Max Length field defines the maximum length of hachuring lines when generating from a single feature and has no effect when hachuring between two features.  The Min Percent field allows you to reduce the length of alternate hachuring lines to a certain percentage.  If you wish all the lines to be the same length, set this value to 100.  The Symbol field defines the symbol that is to be used if required by the type of hachuring generated.

Example of Line Hachuring	Example of Symbol Hachuring

The examples show line hachuring where the Min Percent field has been set to 30 and symbol hachuring where the Min Percent field has been set to 100.  Note that the symbol for the hachuring should be defined as a two-point symbol. The symbol should be drawn in millimetres and n4ce will apply the current view scale to the width of the symbol and the symbol will be stretched accordingly.

The hachuring tool works well on straight or curved features but can cause problems when going around tight corners.  If the hachuring lines would overlap, n4ce gives you the option to pull them back to the angle bisector between the segments.  An example is shown below and this option can be enabled using the Remove Overlaps check button in the hachuring parameters dialog box.  To achieve the required hachuring, it may be necessary to temporarily break and re-join features or to go to the dedicated CAD backcloth and edit the symbols.

The Delete option allows you to delete hachuring symbols that you have created.  You will be asked to indicate the hachuring symbol to delete.  You should ensure that you indicate an element within the hachuring.