Tips & gotchas

Direction depends on the survey direction. The "Down" toggle means the plane goes from your survey's starting point downhill toward the ending point. If you surveyed in the wrong direction, flip the toggle to Up instead of redoing the survey.

Without a survey, the start position is fixed when you tap Start. If you tap Start somewhere other than the planned starting point, the plane is anchored there. Drive to the right starting point first.

Depth Offset to lift or sink the entire plane. If you applied 0.30% downhill but the survey shows the design is 6″ above the ground at the inlet (you want it 6″ below), set Depth Offset = -6″ (or -15 cm). The whole plane drops by 6″.

Volumes are estimates. Bottom Width and Side Slope are used only for the volume calculation. If you don't care about volume, leave them at defaults.

Switching to Slope-IQ. Simple Grading is a flat plane. If your terrain has a low spot or a hump that needs more nuance, you may need Slope-IQ instead. Stop, Reset, change mode to Ditching, and re-design.