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44
44.1
Description
Basic concepts
Geometric elements
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704
Roads - Alignment Editor
Basic Terms
A road surface can be thought of three different types of design elements:
the horizontal alignment
•
the vertical alignment
•
•
the cross section
A'
A''
A'''
TS_051
a
- Natural surface.
b
- The vertical alignment.
c
- The horizontal alignment.
A''/B''
- Points on horizontal alignment
A'/B'
- Points on real surface
A'''/B''' - Points on vertical alignment
Any point A in a project has ENH coordinates in a determined coordinate sys-
tem. Each point has three different positions:
A' - Point on real surface
•
•
A'' - Point on horizontal alignment
A'''- Point on vertical alignment
•
By adding a second point B to the project an alignment is defined. The align-
ment can be thought in three ways:
Horizontal alignment (A''-B'')
•
Projection of the horizontal alignment onto the real surface (A'-B')
•
Vertical alignment (A'''-B''')
•
The angle between the horizontal and the vertical alignment is the grade (a).
A road design is fitted to a base plan or map using the three basic geometric
elements:
•
Straight
Curve
•
Spiral
•
Refer to "I Glossary" for a definition of the terms.
a b c
B'
B''
B'''
Roads - Alignment Editor
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