Technical data

Chapter 4 Working with Drawing and Editing Tools
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For most purposes, you can use the Clothoid spiral. However, when
designing for extremely high-speed travel, such as for the high-speed
rail systems of Europe and Japan, use spirals with quadratic,
cosinusoidal, or sinusoidal curvature functions.
Key Concepts
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Do not try to create spiral curves from the ARC or POLYLINE
commands. You must use the spiral commands to create spirals.
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You can create spiral curves using Speed Tables. A certain amount
of superelevation information, such as the e value, is associated
with the spirals created from speed tables. You can use this
superelevation data in Autodesk Civil Design when designing
superelevated roads.
Special Lines
To help you visually distinguish property features, such as fence and
tree lines, AutoCAD Land Development Desktop has a Special Lines
command that you can use to draw lines or curves using symbol
linetypes. The following illustration shows the treeline special line.
Key Concepts
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It often does not matter which method you use to draw objects—
use the commands that work best for you. The exception is when
you are drawing vertical curves or spirals in designing a roadway.
To draw spirals, use AutoCAD Land Development Desktop spiral
commands and to draw vertical curves, use the Autodesk Civil
Design vertical curves commands.
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After you draw the geometry, you can use the AutoCAD Land
Development Desktop database definition commands to define the
geometry to databases. For example, you can use these objects to
define parcels or roadway alignments.