Filter Points on Line & Grade

Removes points and lines which are not needed to define the geometric shape of the linear objects. Also optionally converts appropriate lines into arcs.

Typical Scenario

Civil designers often export their designs as 3 dimensional lines at very small intervals so that for all practical purposes, the resulting straight line segments represent the design. This results in LISCAD users frequently receiving design files that contain large numbers of potentially redundant points and lines.

This command removes redundant points and lines while still maintaining the geometric integrity of the original design. This puts the data in a far more useful form for export to other systems such as automated grader systems and field based road stakeout software.

The command is display and BLOCK sensitive.

Filter Points on Line & Grade dialog box

Item	Used to
Line Joining
Join Lines	Join lines which have a common end point, are of the same object type and have the same code. Line types supported are straights, arcs and spirals… (Clothoid & Parabolic)
Join lines with different codes	Join lines which have a common end point, are of the same object type and have different codes.
Join lines with different contourable status	Join lines which have a common end point, are of the same object type and have different contourable status.
Construct Objects
Arcs	Replace each part of a line string or spline, containing four or more points which could form an arc, with an arc.
Maximum Radius	Specify the maximum radius that can be used in constructing an arc. Do not set this value impractically large, as it can result in arcs being formed where straight lines are desired.
Geometry Based Filtering
Delete Intermediate 3D Points on line and grade	Delete all intermediate 3 dimensional points that are on the same line and grade.
Delete Intermediate 2D Points on line	Delete all intermediate 2 dimensional points that are on the same line.
Horizontal Tolerance	Specify the horizontal tolerance. A point can be filtered if its horizontal offset with respect to the previous and next points in the line is less than the tolerance.
Vertical Tolerance	Specify the vertical tolerance. A point can be filtered if its vertical offset with respect to the previous and next points in the line is less than the tolerance.
OK	Perform the comparison operation and produce the comparison report.
Cancel	Close the dialog.

Notes:

- If lines being joined are part of two different alignments, each alignment is extended.

- Lines which are included in more than one polygon are never joined. This maintains the integrity of the individual polygons and the lines they share.

- The processing order for each line (assuming the relevant options are selected) is filter points, join lines, again filter points, construct arcs and again filter points.

- To avoid key points such as TP's being filtered, ensure these points are not on displayed groups before performing the filter. Later use of the construct arcs option, with the key points back on displayed groups, should ensure that original TP's are retained as TP's.

- Any displayed rectangles will become arcs if the construct arcs option is selected. Ensure rectangles are not on displayed groups or exclude them with a block to avoid this.