It is calculated from the change in inclination and azimuth between two surveys, and it is reported in degrees per 100 feet or per 30 metres. A high dogleg raises torque and drag, wears the casing as pipe is rotated through it, and fatigues drill pipe or a rod string that is later run through the same bend.
The same change in angle is a higher dogleg if it happens over a shorter distance. A survey station that is too far from the last one hides a local bend by averaging it. Dogleg is a measured-depth property. It is not a vertical curvature.