Examine Chainage and OffsetExamine Chainage & Offset by Alignment

(This functionality is available with the Computations module)
(Not available in LISCAD Lite)

Examines the Alignment Chainage, Alignment Distance, and perpendicular horizontal offset of a point with regard to an alignment object. The results include the perpendicular vertical offset, the perpendicular grade and the elevation of the offset point.

Chainage & Offset dialog box

Item Used to
Alignment Select the required alignment.
Point Select the point or cursor position (by clicking) to be examined. This field is only active if the Static radio button is selected.
Static Select this mode to examine individual points or cursor clicks.
Dynamic Select this mode to dynamically examine the cursor position.
The point field is disabled and points cannot be snapped to while in this mode.
Close Close the dialog box.
Notes When the offset point occurs where the alignment does not have second order continuity, the extended distance (shown in braces) is the distance along a tangent from the point of discontinuity. The offset is the offset from this tangent.

"Second order continuity" means there is a common tangent direction where lines, or line segments, meet.

The shortest distance (or Hypotenuse) to the alignment is displayed below the offset, if this is different.

In the diagram below PTA, YOB and XOA are all right angles. TOA is a straight line.

This command will display the shortest distance to the alignment, regardless of whether of not it is perpendicular to the alignment.


Examine Offset in Wedge
Offset Point:- P
Area of Discontinuity:- X-O-Y
Tangent Line:- AOT
Distance/Chainage:- At O = 11.004
Extended Distance:- OT = 1.756
Offset:- PT = 5.321
Shortest Distance:- PO = 5.603
Dialog Displays:-
Distance: 11.004 {+1.756}
Offset: -5.321
Hypot: -5.603
When a point appears to occur beyond either end of an alignment, a Chainage and Offset may still be reported if the point is perpendicular to any segment on the alignment, or within any XOY area of discontinuity described above.
Examine Offset Past End
Offset Point:- P
Offset Line:- PT
Distance/Chainage:- AO + OT = 17.8
Offset:- PT = 9.8
Shortest Distance:- PT = 9.8
Dialog Displays:-
Distance: 17.800
Offset: 9.800