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---- 3.4.17 Breaklines

Last Updated: 24 March 2022         For: OptiSurface Designer V2.5+

  Breaklines are used to manually edit the topography by adding a line that allows sharp changes in the elevation.  It can be used to fix areas in the Existing Topography and should be used before calculation.  It can also be used to modify the design after calculation such as defining channels or levees.

Breaklines can be imported into OptiSurface Designer in .txt, .xyz and .ags files. The point code must start with '2' or 'L' and have more than one points in a row to be recognized as as a breakline.
40.12055032, -89.20666277, 193.875, L01
40.12747066, -89.20687957, 191.686, L01
40.12789400, -89.19292734, 193.874, L01
40.12135870, -89.19275350, 193.876, L01

Displayed by:
Menu: Tools > Existing Topography > Add Breakline or Tools > Proposed Topography > Add Breakline


For Existing Topography:

For Proposed Topography:

Add Breakline

Click 'Add Breakline' then draw the breakline in the Map. First click will be the first point of the breakline, then the succeeding points will be the next points accordingly. Double click or right click to finish the breakline.

Breakline Options

Right clicking the breakline gives more options to edit and special features as well.


Plot Profile:  Plots the profile of the breakline. Automatically opens up when editing a breakline.

  • Add Reference Line, Curved Line or Offset Line.
  • Calculate Flow - see 3.4.17 Profile.
  • Export - export the profile as image.
  • Report - generate a breakline report as pdf.
  • Edit Breakline - adjust the elevation of breaklines points by click and drag. Or right click to add or delete breakline points.
  • Edit Breakline Table - opens the breakline table as shown below where each cell can be edited as required.

  • Design Breakline - see Design Breakline (OptiLine)
  • Autoscale Axes - adjust the axis scales automatically to cover all points for the Bottom Axis (Horizontal Distance) or Left Axis (Elevation) or Both. This is useful when the Profile is zoomed in.
  • Profile Options - edit the Sampling Spacing, Profile Direction and Add Elevation Labels.

  • Zoom In/Out - zoom in by drawing a window using the middle mouse button and dragging from left to right covering the area to be zoomed in. Drag middle mouse button from right to left to zoom out.

  • Flip - flips the direction of the breakline and profile view.
Edit:  Breakline becomes dashed line enabling drag and drop of the points or vertices in the Map or in the Profile View (see Profile above).

Edit Table:  See Edit Breakline Table above.

Offset:  Offset the breakline; useful in creating the base for channels or levees.

Duplicate:  Create a duplicate of the selected breakline to the Existing or Proposed Topography and shift to a new location.

Move:  Move the breakline to a new location by dropping the breakline to the desired location or editing the coordinates as shown below.

Split:  Split the breakline into two where the breakline was clicked.

Trim:   Trim the breakline to the desired length. Click the breakline where you wish to trim them then select the side you wish to trim off.

Extend:  Extend the breakline to the desired length. Draw the extend line at some distance from the selected pipes.

Connect:  Extends the breakline/s to connect to the selected breakline.

Join Ends:  Join the ends of the selected breakline to another breakline.

Flip:  Flips the direction of the breakline and profile view.

Curved:  Switch the breakline from straight to curved.

Delete: Delete the selected breakline. To delete multiple breaklines, use Delete Breaklines (Polygon Select) as shown below.


  • Curved Line - Switch the straight breakline to a curved breakline.
  • Generated Point - Defines the distance between points along the breakline. These points will be triangulated into the topographic surface. If the points are too far apart, the triangulation may not give desired results. To correct this, reduce the point spacing value.
  • Modify Breakline - Edit the breakline as shown above.
  • Delete Breakline - Delete the breakline.
Help:  Directs the user to this page.

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