To Add Fixed Lines to Alignments

Add fixed lines to build constraint-based alignment geometry for the areas of your design that require maintaining tangency.

After clicking a button on the Alignment Layout Tools toolbar, follow the command prompts on the command line.

To add a fixed line (two points)

The element position is not affected by edits to adjacent elements.

1. Click the alignment. Click Alignment tabModify panelGeometry Editor Find.
2. On the Alignment Layout Tools toolbar, click Fixed Line (Two Points).
3. Specify the start point.
4. Specify the end point. A line preview is displayed.
   Tip: Edit the line direction or location by moving either point or move the line using the middle grip.

To add a fixed line (from curve end, length)

The direction of the line matches the direction of the attachment curve (1). The specified line length (2) is affected only if a floating or free element is attached to it.

The line is straight to the end of the selected fixed or floating element when it is created. If you edit the line or the element it is attached to, tangency is not maintained.

1. Click the alignment. Click Alignment tabModify panelGeometry Editor Find.
2. On the Alignment Layout Tools toolbar, click Fixed Line (From Curve End, Length).
3. Select an element end for the start point and direction.
4. Specify the length. A line preview is displayed.

   By specifying the start point at the end of an element, a direction, and length, you create a fixed two-point line alignment element. The result is a line through two points.

   Tip: You can edit either of the two points or the middle grip, but the initial tangency will not be maintained.

To create a fixed line by best fit

Add the most probable fixed line through a series of using a series of Autodesk Civil 3D points, AutoCAD points, existing elements, or clicks on screen.

Regression points can be added, removed, or modified after the element has been created.

1. Click the alignment. Click Alignment tabModify panelGeometry Editor Find.
2. On the Alignment Layout Tools toolbar, click Fixed Line - Best Fit.
3. In the Line By Best Fit dialog box, select one of the following:
   • From COGO Points. Select two or more Autodesk Civil 3D points. Enter G to select a point group or N to enter points by number. As you select points in the drawing window, an X marks each regression point and a temporary, dashed line is displayed in real time.
   • From AutoCAD Points. Select two or more AutoCAD points.
   • From Elements. Specify the tessellation and mid-ordinate tolerance settings. You can select one or more of the element types listed on the command line. If you selected a profile object, specify the starting and ending station in the Specify Station Range dialog box.
   • By Clicking On The Screen. Select a starting point and at least one other point. You can use OSNAP or transparent commands to select points.

   As you select points or elements in the drawing window, an X marks each regression point and a temporary, dashed line is displayed in real time. Press Enter to complete the command.

4. In the Panorama window, use the Regression Data vista to make changes to the regression points.

   As you highlight a row in the Regression Data vista, the corresponding regression point in the drawing window is highlighted in red.

5. Create the line:
   • Click to create the line and keep the Regression Data vista open.
   • Click to create the line and close the Regression Data vista.