The D-Plane is the science of why the ball flies where it does. When trying to improve your golf swing, there is nothing – absolutely nothing – more important than to understand why the ball flew where it did.
Euclid, the famous mathematician, said any two lines that intersect form a plane. Theodore Jorgensen, the author of the Physics of Golf book calls the plane formed by the direction of the face at impact and the direction of the path of the club at impact the D-plane.
The “D” stands for “descriptive” of the plane that the impact takes place. The ball’s initial launch direction starts on this plane. The golf ball spins around 1 axis. This spin axis is always perpendicular to the formed D-plane.
So if the formed D-plane is vertical (which means the clubface and path are going in the same direction) the spin axis is parallel to the ground. If the path of the club and the delivered face angle do not match then the created D-plane is tilted and the spin axis is tilted and the ball will curve. This is only true for a center-faced impact. (For now we will assume a center face impact. We will introduce the off center effects later.)
The ball starts on the D-Plane approximately 70% toward the face orientation for short irons and about 85% toward the face orientation for the driver. It then rises up the D-Plane and gravity eventually pulls the ball down off the D-Plane if the D-Plane is tilted. If the D-Plane is vertical then gravity will pull it down on the D-Plane.
Path & Face both Pointing Toward the Hole at Impact
Horizontal Spin Axis
The Draw or Hook Shot
Face Pointing to the Left of the Path at Impact
Left Tilted D-Plane
Left Tilted Spin Axis
Right to Left Curvature
The Fade or Slice Shot
Face Pointing to the Right of the Path at Impact
Right Tilted D-Plane
Right Tilted Spin Axis
Left to Right Curvature
So it is the D-Plane that the instructor and student must understand, measure, and adjust to improve ball striking. The interesting thing is that really none of the 4 ball flight components or the 4 impact alignments can be accurately measured by a video camera. But 7 of the 8 are measured and calculated by Trackman.