Design Line Features – AppsinCadd

The Design Line options allow you to use design line features to attach further information to other features. Design lines are features that are assumed to represent some form of design such as a road or rail alignment. They normally have design information, such as chainages, bearings or radii, attached to them. For instance, if an MX Master string is read into n4ce, this information is stored in the dimensions attached to each point. The dimension used for a chainage is CHN, for a bearing is BRG and for a radius is RAD.

Feature Projection

The option Feature Projection allows you to take a design line and project that out to other features or CAD information. New points will be created and these will be either inserted into existing feature strings or appended to new ones. When this option is selected, the dialog to the right is displayed.

The Method group defines the type of projection that is carried out. Depending on which method you choose, the other items of the dialog are enabled or disabled.

Projecting Chainages to Features

The To Feature method of projection takes the design line and projects its points onto another feature. These new points are then inserted into the indicated feature. Each of these points will have a chainage dimension added to it, the value of which is the chainage of the projected point from the design line. The name of the chainage dimension will be the code of the design line feature rather than the normal CHN.

In the example shown below, the design runs along the bottom of the image. It has been projected to the features representing a slip road and new points will be created on these features where there is a blue square. The heights for the new points are interpolated from the points on either side.

Projecting at a Gradient

The At Gradient method of projection takes the design line and projects its points onto another object at a user nominated gradient. This will create a new feature that will be above or below the reference object.

The object being projected to is either a line feature or a CAD polyline. The CAD polyline can either be in a CAD backcloth or the dedicated CAD backcloth for the current model. This is specified in the Reference group. The code of the new feature is defined in the Code combo box and if the gradient is necessary, it is defined in the Gradient combo box.

Projecting Through a Feature

The Thru Feature method of projection takes the design line and projects its point onto an object through another feature. When passing through this other feature, it can calculate the gradient that is required. This will create a new feature that will be above or below the reference object.

Design Line Dimensions

The Dimension options allow you add dimensions to feature strings to, in effect, turn them into design lines. When selected, you will be asked to indicate the feature and the appropriate dimension added as follows.

Chainages Each point of the feature will have a chainage dimension, CHN, added to it by calculating its distance along its feature. You will be asked to enter the start chainage for the feature and this value will be added to any distance along. If the first point already has a chainage dimension, this value is displayed as the start chainage.

Bearings Each point of the feature will have a bearing dimension, BRG, added to it by calculating the direction of the feature at each point. This bearing will consider curve fitting. However, if no curve fitting is applied to the selected feature, the bearing value is assumed to be the average of the segments leading in to and emerging from a point.

Radii Each point of the feature will have a radius dimension, RAD, added to it. This radius will consider any curve fitting. If no curve fitting is present, the radius value is calculated from an arc passing through the point and those immediately before and after it.

6D String Each point of the feature will have all three of the dimensions above added to it.

Note that a more accurate value can be determined for the chainage if the feature that you are adding dimensions to has been curve-fitted.

Filtering Chainages

When importing strings from MX GENIO files, the master strings often have too many points. For instance, a point may have been generated on a master string at every 1m and you only interested in points every 5m. The Filter Chainages option allows you to filter out the unwanted points. After you have indicated a master string, n4ce will determine the current interval of points on the string and a dialog box will be displayed showing the current interval and asking for a new interval.

When filtering the points, only the points at the old interval that do not match the new interval will be filtered. Any points at chainages that do not match the old interval will also remain. These usually represent the start and end of horizontal or vertical elements.