Graphics Programs Reference
In-Depth Information
Applying Corridor targets
One thing that makes corridors so powerful is their ability to interact with other
objects in the drawing. Corridors are able to morph themselves into different
shapes and sizes in order to respond to existing features or components of newly
designed features. This is made possible through the use of special subassemblies
that can be stretched, twisted, and reconfigured as they progress along the corri-
dor. What makes these subassemblies special is that they utilize corridor targets .
Three types of targets can be applied to a corridor: surface targets , width or
offset targets , and slope or elevation targets .
understanding Surface targets
Surface targets are used in a number of cases where the corridor needs to inter-
act with a surface, such as when a slope is projected from a design elevation
to the point where it intercepts an existing ground surface. This is referred to
as daylighting . For example, in a section of road design that is above existing
ground, daylighting can be used to create the embankment from the elevation
of the road to the original ground elevation (see Figure 9.8).
Road
3:1 Slope
3:1 Slope
Existing Ground Surface
Daylight Point
Daylight Point
FiGuRE 9.8 A cross-section view of a road that shows the daylighting of a
3:1 slope on either side
Although daylighting is the most common example of surface targeting, there
are other examples such as establishing the cross slope of an existing road, setting
the top elevation of a retaining wall, setting the depth of a pipe, and many others.
understanding Width or offset targets
Another type of target used in corridor design is referred to as a width or offset
target . As the name suggests, this type of target is used to vary the width of
an object or the distance between a point and the centerline (also known as
offset ). For example, an alignment can be used as a target that controls the
outside edge of a lane. As the path of the alignment moves away from the road
centerline, the lane widens. As the path of the alignment moves toward the
road centerline, the lane narrows (see Figure 9.9).
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