Creating Linked Features Lines from Corridors
Introduction
In Civil 3D versions older than 2009, if a user chose the
option to create a feature line from one of the links of a
corridor, that feature line was cast into the design world
with no trail of bread crumbs back to the safety of its
creator, the corridor. That feature line was considered
static and if the corridor changed, those changes did not
reflect through to the feature line. In most cases, the
prudent solution would be to erase the feature line and
recreate it with the new corridor geometry. To make matters
worse, if there were any design elements that relied on the
feature line, such as grading objects, then those entities
would have to be revised or recreated as well.
With the release of the 2009 version, users now have the
ability to create feature lines from corridors that stay
linked to their parent corridors. If the corridor were to
change, then the linked feature lines change as well. This
is particularly useful to the designers who create
subdivision lot grading with feature lines rather than with
corridor subassemblies. The main idea is to use a corridor
feature line created from the back of curb or sidewalk to
launch the lot grading. The designer can allow the free
triangulation among the feature lines created for building
envelopes, ditches, swales, ridges, and slopes to create a
proposed surface covering the lots.
Application
Once a corridor has been created in a drawing, the user can
select the Create Grading Feature Line from Corridor tool
from the Corridor > Utilities pull down menu.
In the example above, the corridor was created with the
outermost links being the outside edge of sidewalk. This is
where our lot grading will begin.
Once the tool has been chosen, the user must select the link
(running parallel to the alignment) on which to create the
feature line. If two or more links are stacked on top of one
another in three-dimensional space, then the user will have
the opportunity to pick the correct link from a list. Once
it has been identified, the Create Feature Line from
Corridor dialog box will pop up with several choices.
The user can choose the site to attach the feature line to,
create a name for this particular feature line, apply a
style to the feature line, assign it to a layer, choose to
smooth the feature line, and check whether or not the
feature link will stay linked to the corridor. In this case,
I have chosen to name the feature line and keep it linked to
the corridor; all other options are default. Hitting the
OK button here will create the feature line and allow the
user to select another link. Hitting the return key here
will end the command. This feature line may now be used to
create lot grading on the right side of the corridor, and if
any part of the corridor changes we can rest assured that
the feature line will update itself as will the grading
which depends on it.
Conclusion
Often times, our designs are more intricate than the uniform
grading offered by the Daylight subassemblies. The feature
line option gives the designer a bit more flexibility to
shape the terrain he or she is designing. As an applications
engineer, I am often asked about the best way to create
roadside ditches that meander or have profiles that are
independent of the road profiles. I can now reasonably
suggest the option to shape that ditch flowline with a
feature line, then have the ditch banks dictated by the
simple triangulation between that flowline and the feature
line (and subsequent grading) created from the corridor.
As designers and Civil 3D users, we are always looking for
different ways to accomplish our daily tasks. Sometimes we
settle back into our old ways if new techniques do not
create a boost in efficiency, sometimes the new methods get
assimilated into our bag of tricks. In this case, I think we
will see more of the latter.
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