The science behind the score.

How far the hips turn away from the ball and back through. The base of the coil and the first link in the sequence.

Shoulder turn — the larger of the two rotations, and the one that stretches the core against the hips.

Shoulders minus hips — the separation that stores elastic energy in the trunk. The single most-cited power measure in the literature.

The extra separation gained just after the downswing starts, as the hips fire while the shoulders stay coiled — the stretch-shortening that releases like a sling.

How steep or flat the shoulders sit at the top. Positive means the trail shoulder is the higher one. As much a consequence of build and setup as of what the golfer did, so it's read beside address posture.

The order and timing of peak rotational speed up the chain — hips, chest, lead arm, club. Out of order is the classic "casting" pattern.

The sequence's own numbers, each a metric in its own right: how fast each link peaks, when the arm and club peak against impact, and when the hips and then the chest stop turning back and start down. Each link should be faster than the one before it, and the hips should start down first. A reading is reported only when its peak could be placed; absent means it could not, never zero.

A session reading: the share of swings whose four peaks came in the professional order. It counts only swings whose peaks were all placed, and quotes the generous end of what that count supports, so a short session is never accused of an order it hasn't shown.

How much the instants of the hips', chest's and lead arm's peaks wander across a session, against how much they wander for touring professionals (19, 14 and 8 ms). It says nothing about any one swing's timing, only about how well it repeats.

Lean of the spine away from the target at impact — the hip-to-shoulder line measured from vertical in the face-on plane.

Shoulder line against hip line. Too little goes with a steep, over-the-top delivery; too much throws the low point behind the ball.

Lateral travel of the head through the swing. A little back-and-through is normal; only excess is a fault. Read beside pelvis sway to tell a head move from a whole-body slide.

Rise or dip against address height. An early rise through the downswing is the visible half of standing up out of posture; a dip is a drop into the shot.

Change in eye-line angle from address. Small and stable is normal; a large or abrupt change tends to accompany a loss of posture.

How much the golfer is bent over from the hips, and whether that angle is held. It lives in the sagittal plane — present in a face-on image but foreshortened to noise by the projection.

The same forward bend, read along the back from the base of the spine to the back of the neck — the line a TPI coach draws — off the outline of the body rather than the hip and shoulder joints. That is what lets it hold at the top, when the shoulders turn away from the camera.

Standing up through the ball, seen face-on. A trunk bent over the ball leans toward the camera and looks shorter; as the golfer stands up it looks longer. So the hip-to-shoulder line's length against address is the face-on view of lost forward bend.

How far the head rises or drops against address, from the second camera. A head that comes up on the way back is the golfer standing up out of posture. Read on the midpoint of the ears, which holds its height while the head turns — the nose alone climbs several centimetres at the top on a head that hasn't moved.

How the head is carried against the trunk at address: chin tucked down toward the chest, or held up and away from it. Measured against the trunk, so bending over the ball doesn't move it.

Heel-to-heel span, expressed against the golfer's own shoulder width rather than in millimetres — so a tall player and a short one are judged on the same scale.

Where the ball sits in the stance, as a fraction of stance width from the lead heel. Read against the club in hand, never against one ideal.

How far the ball sits from the toes, less the part the club accounts for: the club's length laid along the line from the hands to the ball, at the angle the camera actually sees. What is left is how far past the toes the hands sit, which stays about the same from wedge to driver, so one range serves every club. Too close crowds the arms and steepens the swing; too far pulls the shoulders forward and rounds the back.

How far each toe points out at address. More lead-foot flare makes it easier for the lead hip to clear through the strike — a setup lever for a golfer who struggles to finish the turn.

Stance alignment — open, square or closed. Measured face-on, so it reads the apparent line; a down-the-line view would resolve true target-line alignment.

How far the lead heel comes off the ground around the top. A little is common and can free the turn; keeping it down is a legitimate stylistic choice.

How far the body's centre sits from the lead ankle at the finish — still hanging back, or fallen through it. A balanced finish is the low end.

Side-to-side travel of the hips along the target line: slightly away from the lead side going back, then a drive toward it coming down, returning near zero by impact.

The pelvis centre rising or sinking as a whole. A small controlled push up into impact adds speed; an early or excessive lift pulls the club off its path.

How far the trail hip sits above the lead hip at the top. Deliberately an absolute angle rather than a change from address, because the figure it's read against is absolute — everyone has some.

Where the hips sit over the stance, dropped as a vertical line and measured in inches against the ball. Read first at address against the club's own corridor, then read the travel: the hips move lead-side through every good downswing.

The chest's counterpart to pelvis sway, same sign convention — the two are read together, because the same absolute movement means something different at each end.

The lead knee's sideways travel minus its own hip's — a difference, deliberately, since pelvic rotation carries the hip across anyway. A large value at the top is the observation.

Movement of the hips toward the ball — the classic "early extension" that crowds the arms and forces you upright. It lives on the depth axis a face-on camera is blind to.

How far the backside moves toward or away from the ball against address, in centimetres, read on the back edge of the body at hip height — the butt line a coach draws. The hips turning doesn't move it the way it moves the hip joints.

Flexion (bowed, palm down) versus extension (cupped) of the lead wrist — the main control of clubface angle, since the back of the lead hand mirrors the face.

Radial (cocking up) versus ulnar deviation — how the wrist sets the hinge, holds the lag, then releases it. The lateness of the release into impact is the marker of good timing.

Axial rotation of the lead forearm — the "roll" that squares the face through impact.

The same axis stated as a change from address, which is the honest way to read it: the absolute value is meaningless across sessions, because it depends on whatever posture address happened to be. Large, late pronation into impact is flipping.

How straight the lead arm stays, from the shoulder, elbow and wrist geometry. A bent, lifting lead elbow late is the "chicken wing".

When a HackMotion wG3 is worn, its three readings are recorded under their own keys beside ours rather than in place of them — so which instrument graded a swing stays recoverable after the fact.

The gap between the lead upper arm and the chest, widest somewhere between address and the top. Some separation is normal — zero would mean the arm is pinned, which is its own fault.

How far the hands stay from the body at the top, expressed against the golfer's own arm length — a fraction of the width actually available to them rather than an absolute distance.

How far the trail elbow has risen above the shoulder line at the top — the "flying elbow" made into a number, normalised by shoulder width so it means the same for any golfer.

The arm-to-body angle through the strike. A rising angle after impact means the arm is separating from the body rather than extending down the line.

The trail wrist's extension that "holds the tray" supporting the club. Flattening it too early is the same throw/flip event the lead wrist shows — used to corroborate the face reading and raise confidence.

Trail elbow against lead elbow, at address and at impact. The change between the two shows how the arms fold, rotate and re-deliver — the trail elbow tucking on the way down, for instance.

Which way the trail elbow points at the top. On most golfers it points at the ground, under the hands, where it supports the club; a flying elbow points well behind the golfer. The down-the-line view sees it where the face-on shoulder line collapses with the turn.

How the arms hang from the shoulders at address, against straight down. Arms that hang naturally sit close to vertical; hands pushed out toward the ball are reaching, and hands pulled in under the body are tucked.

Speed of the clubhead at impact, differentiated from its path in the face-on image and scaled by the ball-diameter ruler. A second camera, or a sensor on the shaft, would restore the depth component of its velocity.

Speed of the grip. In a good release its peak comes slightly before impact — the hands slowing is what lets the clubhead sling past. Hands still accelerating at impact means a late release or a stalled body.

The angle between the lead arm and the shaft through the downswing. Casting widens it early and throws away speed; holding it too long leaves the face open.

How far the shaft leans forward at impact. Hands ahead of the ball is typical and desirable for irons; the driver is played with the shaft near vertical or leaning back. Too little on an iron is an early release, with thin and fat tendencies.

Swing length, as an angle. Zero is parallel to the ground, positive is past parallel. Strongly club-dependent and partly a matter of flexibility and style — so the corridor is wide and a reading outside it is a conversation, not a verdict.

Whether the clubhead is moving down or up at impact — the vertical angle of its travel, read from the tracked club in the face-on plane.

How far target-side of the ball the clubhead bottoms out its arc, signed in inches. Positive is a low point ahead of the ball — the descending, ball-then-turf strike an iron wants; negative sits behind it, wrong for an iron but exactly right hitting up on a driver. A delivery number a launch monitor doesn't report directly.

The same low point, worked out instead from a connected launch monitor's attack angle and the radius of the club's arc — far more precise than the camera's. Each degree of descending attack puts the low point about an inch further ahead with a mid-iron. When a monitor is connected, this is the low point read first.

Whether the club steepened or shallowed between backswing and downswing — over-the-top, quantified. Positive is steeper.

The horizontal direction the clubhead travels through impact relative to the target line — in-to-out (+) or out-to-in (−). The discriminating axis is the one pointing at the camera, which is exactly what a face-on view cannot see.

The tilt and direction of the best-fit plane the clubhead travels on through the downswing — a genuinely three-dimensional object.

The same fitted planes read as angles to the ground: the backswing plane from address to the top, and the downswing plane from the top to impact. Swing plane is measured against the golfer's own address, so a golfer who sets up flat and stays flat reads as on plane; this one shows them flat all the way through. Graded against a norm for each kind of club, because a driver swings on a flatter plane than a wedge.

The plane through the ball's target line and the hands, through the whole swing. At address it starts on the shaft; at the top it is the swing plane. Hands that move out toward the ball from the top steepen it — the over-the-top move — even when the club drops back under them before delivery. Its steepening is how much steeper the hands come down than they went up, at the same height.

The plane from the ball through the trail shoulder at address: the steep edge of the slot, with the address shaft as its flat edge. A club travelling above it is steep; one dropping below where it was set at address is under the plane.

How upright the shaft stands, seen from down the line: its angle to the ground at address and again at impact. The change says whether the club came back steeper or flatter than it was set up. Most golfers return it a little steeper; a big steepening with the toe digging in is the dynamic-lie fault.

Where the hands come down against where they went up. Seen from down the line, hands that come down outside the path they went up on are the over-the-top move, and the most direct picture of it there is — the club has to come back across the ball from out there.

Ball speed, spin, launch, face angle, face-to-path, strike location and the rest, read out of a connected monitor — a Foresight GCQuad through FSX2020 (or Foresight Premier, from the build after beta 6), or any device speaking GSPro Open Connect (Garmin R10, Rapsodo MLM2PRO, SkyTrak+, PiTrac). They are live readings, not promises — and they carry an lm. prefix precisely so that a measured number can never be mistaken for one of our estimates.

Start line and curvature combined into one signed reading: positive started and curved right, negative both left. A pull-fade reads exactly zero, not a small number — the halves cancelling is what makes it a different shot, and saying so is the point.

Our own optical estimates of what the monitor measures. They need a ball-flight tracker; what we have today is an at-spot presence detector, which is a different instrument.

How long the backswing takes, from address to the top — read straight from the swing's phase events, so it needs no particular device.

Backswing time divided by downswing time — the rhythm of the swing, and a number that's remarkably consistent among good players.

The headline for the wrist analyzer — higher is closer to the reference. Read it, then drill into the individual wrist metrics to see what moved it; most often it is a cupped lead wrist at the top.

How closely the wrist action matches each of three archetypes, scored independently. The headline is the best match; the trio tells you how decisively. Within a few points and it is flagged "blended".

The whole-swing counterpart to the wrist score: one 0–100 rating of how the swing adheres to the reference. The scorer and its full-swing bands are the piece still being seated on real data.