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CHAPTER 1 The Basics of auTocaD civil 3D
Creating Curves
Curves are an important part of surveying and engineering geometry. In truth, curves are
no different from AutoCAD arcs. What makes the curve commands different than the basic
AutoCAD commands isn’t the resulting arc entity but the inputs used to draw the arc. Civil 3D
wants you to provide directions to the arc commands using land surveying terminology rather
than with generic Cartesian parameters.
Figure 1.30 shows the Create Curves menu options.
Standard Curves
When re-creating legal descriptions for roads, easements, and properties, engineers, surveyors,
and mappers often encounter a variety of curves. Although standard AutoCAD arc commands
could draw these arcs, the AutoCAD arc inputs are designed to be generic to all industries.
The following curve commands have been designed to provide an interface that more closely
matches land surveying, mapping, and engineering language.
cr e a t e cu r v e be t w e e n tw o li n e s co m m a n d
The Create Curve Between Two Lines command is much like the standard AutoCAD Fillet com-
mand, except that you aren’t limited to a radius parameter. The command draws a curve that is
tangent to two lines of your choosing. This command also trims or extends the original tangents
so their endpoints coincide with the curve endpoints. The lines are trimmed or extended to the
resulting PC (point of curve, which is the beginning of a curve) and PT (point of tangency, or
the end of a curve). You may find this command most useful when you’re creating foundation
geometry for road alignments, parcel boundary curves, and similar situations.
The command prompts you to choose the first tangent and then the second tangent. The
command line gives the following prompt:
Select entry [Tangent/External/Degree/Chord/Length/Mid-Ordinate/
miN-dist/Radius]<Radius>:
Figure 1.30
Create Curves
commands
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