Dip

The true dip of a surface is the angle drawn from horizontal that it makes with a horizontal plane - the angle being measured in a vertical plane that is perpendicular to the strike of the surface. Apparent dip is the angle measured in any other direction. Given the strike and an apparent dip, or two apparent dips, it is possible to obtain the true dip. In geological work, the dip of a bedding plane or other planar structure cannot usually be measured with an accuracy greater than ±1°, and in many cases dips are recorded which are generalised in amount and direction. A clinometer is used for measuring dip.

Regional dip is a generalised statement of the direction of dip over a region, ignoring minor (local) variations of dip amount or direction.