Modifying the horizontal geometry
There are two alternative goals for modifying the horizontal geometry:
•obtaining a continuous curvature geometry. This means that the geometry includes transition curves between a line and a circular arc as well as between circular arcs with different radii. At the moment, the only supported transition curve type is a clothoid.
•obtaining continuous tangent geometry. This means that the geometry contains lines and arcs but no transition curves.
The application fully supports geometry where a set of curved components with continuous curvature is connected with a line to another set of components with only continuous tangent.
The changes in the geometry can be followed by viewing the changes in the Component fitting main window, the Road fit: results dialog, and in the graphical display of the geometry components in CAD views. Additionally, you can display exaggerated residual vectors by using the Tools / Residual display command.
The workflow for producing a horizontal geometry given below aims at obtaining a continuous curvature geometry that represents the line string. The modification steps for going from a preliminary geometry to the final geometry may include in some order the following steps:
Basic workflow
1. Change circular arcs to lines.
Tools / Remove arcs with large radius
2. Break-up curved sets with a change in the sign of curvature.
3. Join circular arcs with similar radii.
Tools / Join arcs with similar radii
4. Add transition curves, change the mode of the curved set from continuous tangent to continuous curvature (or back).
Tools / Change curved set mode
Done repeatedly during the basic workflow
1. Refit the line components.
Regression / Refit selected lines
2. Refit individual circular arcs or join several components into an arc.
Regression / Refit selected components as arc
3. Refit the lengths of all components.
Regression / Refit component lengths
4. Find an alternative set of components for a segment of the geometry
Tools / Fit alternative components
Finalizing
In the very last part of the geometry modification process, the radii of the circular arcs can be changed to desired values.
