Grading in civil engineering and landscape architectural construction is the work of ensuring a level base, or one with a specified slope, for a construction work such as a foundation, the base course for a road or a railway, or landscape and garden improvements, or surface drainage. The earthworks created for such a purpose are often called the sub-grade or finished contouring.
The Denny Regrade in process, Seattle, Washington (1900s).
Regrading for a subdivision in the Santa Monica Mountains, Los Angeles, California (1970s).
Modern road grader
The grade (US) or gradient (UK) of a physical feature, landform or constructed line refers to the tangent of the angle of that surface to the horizontal. It is a special case of the slope, where zero indicates horizontality. A larger number indicates higher or steeper degree of "tilt". Often slope is calculated as a ratio of "rise" to "run", or as a fraction in which run is the horizontal distance and rise is the vertical distance.
25% ascent warning sign, Wales
30% descent warning sign, over 1500 m. La Route des Crêtes, Cassis, France
A trolleybus climbing an 18% grade in Seattle
Ascent of German Bundesstraße 10