The SGRD command datum-adjusts existing Civil-3D Points, using a temporary grading line drawn through pick points.
Type SGRD at the command line, and select the points you wish to change. Or select the points that you wish to change, right-click, and select "SincpacC3D Point Commands->Datum Adjust Points->Straight Grade Using Points" from the shortcut menu.
You will then be prompted to select the grading points. You have several options at this point. If your points are in 3D, you may use the NODE OSNAP to snap to the nodes of Points. Or you may use the 'PO transparent command to select points and use the point elevation, even if your points are flattened to Z=0. Or you may snap to 3D-linework. Or you may enter "E" to hand-type an elevation, then pick a point on-screen to select the horizontal location, or "SE" to adjust the Grading Settings.
Consider the diagram below.
Now assume we wish to raise the grade of point 4821 by one foot, and straight-grade back to a 7118.78 at point 4817. To start, we select point 4821 and datum-adjust it upward by 1 foot, using the normal Civil-3D datum-adjustment command. We then start the SGRD command, and select points 4818-4820. At the prompt to select the grading points, we use the NODE OSNAP or the 'PO Transparent Command to select points 4821 and 4817. The result is shown below.
Datum-adjust points based on Feature Lines, 3D-Polylines, Survey Figures, or other linework.
Datum-adjust points based on Profiles.
Straight-grade points, using an existing piece of linework as a temporary alignment for the grading.