The most commonly used method to express the slope, that is, the percentage of the height difference between two points and its horizontal distance, is calculated as follows: slope = (height difference/horizontal distance) x 100%. When percentages are used, I = h/l x 100%.

For example, a slope of 3% means that the horizontal distance rises (falls) by 3 meters every 100 meters; 1% means every 100m in the horizontal direction and every 1m in the vertical direction. And so on.

Degree method: the slope is expressed in degrees and calculated by inverse trigonometric function, and its formula is as follows: tanα (slope) = height difference/horizontal distance.

So α (slope) =arc tan (height difference/horizontal distance)

Degree method

The gradient is expressed in degrees and calculated by inverse trigonometric function, and its formula is as follows:

Tanα (slope) = height difference/distance

So α (slope) =arc tan (elevation difference/distance)

Tangent and sine slopes of different angles

Angular tangent sine

0 0% 0%; 5 9% 9%; 10 18% 17%; 30 58% 50%; 45 100% 7 1%; 60 87%; 90 ∞ 100%