Closed Ditch¶
Use this dialog to define closed ditches.
Where can I find the dialog?¶
In the toolbox, select SFI Properties..., go to the Road Body tab, and open the Closed Ditch table.
An open ditch is usually defined in the surface descriptions table. Here, surface group 4.x is used to connect the shoulder to the terrain surface.
Layers for Ditch¶
In a single profile, you can describe several separate closed ditches.
Figure: Example of closed ditches
You create new ditches by clicking New... in the first window.
The following layers are intended for closed ditches:
- Layer 41: Closed ditch
- Layer 42: Closed ditch 2
- Layer 43: Closed ditch 3
You can also select a user-defined layer.
Description of Ditch Alignment¶
You specify the ditch alignment in the second window, i.e., in the columns for profile and type.
You define a ditch alignment with at least a start and end profile. This applies, for example, to ditches with the same design along the entire section. You create a profile by selecting New with the right mouse button.
Between the start and end profiles, you specify profiles where the cross-section of the ditch should change. Between two profiles with different ditch cross-sections, the program interpolates linearly.
Figure: P1 = start profile, P4 = end profile
You indicate a gap in the ditch alignment with a - (minus/hyphen). Enter this in the profile column after the end profile. This tells the program that the sub-section stops here.
The depth of the ditch is calculated from relative heights (type REL) or absolute heights (type ABS). If relative heights and the same value are used along the entire section, the ditch bottom will have the same vertical curvature as the centerline.
Description of Ditch Cross-section¶
The breakpoints in the ditch cross-section are defined by distance from the centerline and height, either as absolute height or relative to the centerline.
You create the breakpoints by selecting New with the right mouse button in the third window. Be sure to enter the points in natural order, from left to right. If the distance is given as a negative value, the ditch is to the left of the centerline.
Ending the Ditch Surfaces¶
The program finds the intersection point between the ditch walls and the trough. If the ditch is placed outside the road area, it will end where the walls intersect the terrain surface.
Figure: Intersection point between ditch walls and trough
In cases where the ditch is defined so that there is no intersection as described above, the ditch walls will be extended to the intersection.
Figure: Extension of ditch walls to intersection