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Chapter 3 Working with Profiles and Vertical Alignments
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2 In the Sample offset tolerance box, type the sample offset tolerance.
Profile elevations are calculated at each point that the horizontal alignment
crosses a surface triangle edge. To improve profile definition in areas with large
surface triangles, this value determines whether supplemental elevations are
sampled along curves and spirals.
The sample offset tolerance dictates how large the mid-ordinate distance of a
curve or spiral can be between sample points. The default is half a unit. This
means that if the traced chord is more than half a foot or meter away from the
actual curve, then the command samples additional elevation so that the chord
for each curve segment does not exceed the sample offset tolerance (half a foot
or meter) away from the curve. This only affects the rate at which the existing
ground elevations are sampled on a curve. The actual profile always follows the
true surface exactly.
3 Under Sample Lines, select the Import check box to place sample lines in plan
view so you can see the locations that are being sampled.
The sample lines are imported onto the specified layer even if the layer is
frozen. Importing sample lines is useful to verify that the graphic representation
of the alignment in the drawing matches the alignment database file.
When the Import check box is selected, the Layer box becomes active.
4 In the Layer box, type the layer for the profile sample lines.
5 Under Left and Right Sampling, select the Sample left/right check box to sample
the left and right offsets of the alignment.
If this box is not selected, then only the profile centerline is sampled.
6 In the Sample left offset and Sample right offset boxes, enter sample offset
values.
Normally you enter positive values for left and right sides. If you use a negative
value, then the sampling is done on the opposite side of the alignment. For
example, if you specify -10 for the left sampling width, then the command
samples 10 units to the right of the alignment. The sample offset widths cannot
be greater than the smallest radii of the alignment.
When sampling left and right of the alignment, the command gives slightly
inaccurate data at PIs (Points of Intersection) that have no horizontal curve due
to overlapping or disjunct offset lines.
7 Click OK to save the sampling settings.
Changing the Existing Ground Layers Settings
for Profiles
To change the existing ground layers for use with the Profiles commands, use
the EG Layers command. You can assign each existing ground profile definition
to a separate, unique layer. If you intend on having more than one profile in a
drawing, then set these layer names to unique names before creating each
profile for easier layer management.
These layer settings are stored with the invisible profile block that is created
when you generate a profile. You cannot change these settings for a profile after
the profile has been created in the drawing. If you want to update a profile with
these changes, then you must recreate the profile by using the Full Profile,
Surface Profile, or Quick Profile command.