The science behind the score.
A good swing number isn't a verdict handed down from a black box — it's a measurement you can trace back to the movement that produced it. This is how PinPoint Studio reads a swing, the biomechanics it scores against, and the maths that keeps a single number honest.
This page explains the approach. The wrist analyzer and the full-body kinematics pipeline both produce real output today — 52 of the catalogue's 95 metrics — and are being checked against a hand-annotated corpus of real swings before any of it is released. The whole-swing score is the piece still being seated on real data. Nothing here is a finished, dependable product yet — that's deliberate. See how we earn the numbers →
From frames to a score
To map a swing in milliseconds, each shot runs through a sequence of stages — every one building on the last, from raw pixels up to a coachable number.
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Pose & object detection
The analysis pass runs a whole-body pose model over the frozen swing — 133 landmarks: body, feet, face and 21 per hand — while the club and ball are tracked separately. (The lighter skeleton you see drawn live during capture is a different, faster model, and no measurement is taken from it.)
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Fusion & smoothing
The whole-body track is filtered by an offline smoother and fused with the IMUs' high-rate motion data on one shared clock — resolving the jitter and gaps a single frame can't. A second, down-the-line camera will later add the depth axis.
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Skeleton, scores & faults
Events are anchored on impact, metrics are computed against coaching bands, and faults are ranked by how many points they cost — each with a plain-English drill.
Illustrative — the analysis pipeline, stage by stage.
Full numbers from a single camera
The system adapts to whatever hardware is in the bay — a single calibrated camera with motion sensors is a first-class setup, not a fallback. More kit sharpens the picture.
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One face-on camera
A single face-on view already carries most of the catalogue — posture, the head, stance and balance, rotation and X-factor, club delivery and tempo. Adding wrist sensors is what makes the wrist angles instrument-grade rather than inferred.
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A second, down-the-line camera
Resolves depth the single view can't, unlocking the depth-axis measures — club path, launch direction and a true 3D swing plane.
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A sensor on the club
A light sensor on the shaft gives direct club-head speed and shaft lean without needing the second camera.
Illustrative — sensor placement and a face-on camera.
The power coil: X-factor
Speed in golf isn't arm strength — it's elastic tension stored in the core, which we measure in degrees of separation between the shoulders and hips.
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The backswing coil
The difference in rotation between shoulders and hips at the top. A strong coil separates the two by roughly 40–50°, stretching the core.
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The downswing stretch
As the downswing starts the hips turn first while the shoulders stay coiled, briefly increasing separation — a stretch that acts like a released sling.
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How to use it
A low coil usually means the hips are drifting or over-turning — work on hip stability. A weak stretch means starting the downswing from the ground up, not the upper body.
Illustrative — separation of shoulders and hips, viewed top-down.
The kinematic sequence
Like cracking a whip, speed travels through the body in a specific order. Each segment peaks, then brakes to pass its energy to the next. This one is not measured yet — the phase ladder and the tracks it needs are both in place, but the angular-velocity series the sequence is read from are still to be built.
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The proper order
Energy peaks bottom to top: hips → chest → lead arm → club. Each segment acts as a pivot, handing speed forward.
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Peak, then brake
To transfer speed a segment has to decelerate rapidly. When the hips brake, that energy surges into the chest; when the chest brakes, it snaps into the arms.
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Out of order
If the shoulders or arms peak before the hips, the swing is "casting" — speed bleeds away, the path changes and slices follow.
Illustrative — peaks fire proximal to distal, in order.
Lead wrist: flexion & extension
The clubface direction is governed by the lead wrist — the one movement read straight from the IMUs and the first analyzer producing real output today.
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Flexion (bowed, palm down)
Bowing the lead wrist rotates the face closed. For a slicer, more flexion helps square or close it.
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Extension (cupped, knuckles up)
Cupping the wrist rotates the face open. Excessive cupping is the most common cause of weak, high slices.
- 3
Radial / ulnar hinge
Cocking the wrist up stores the lag through the downswing; releasing it down snaps the club square at impact.
Illustrative — lead-wrist flexion vs extension and the face.
Sway, thrust & lift
Consistency means turning around a stable spine angle — not swaying side to side or thrusting the hips toward the ball. Two of the three are measured face-on today; the third is the clearest example on this page of a metric a single camera physically cannot deliver.
- 1
Sway (side to side)
A small shift away from the target in the backswing, then a strong drive back toward the target coming down. Too much either way costs strike.
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Thrust (early extension)
Hips moving toward the ball crowd the arms and force you to stand up out of posture — a big source of blocks and shanks. It moves along the axis pointing at a face-on lens, so it takes a down-the-line camera: no amount of cleverness recovers a movement the projection collapsed to nothing.
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Lift (up and down)
Hold your height through the backswing, then push off the ground into impact — controlled vertical lift is a source of power.
Illustrative — a good drive vs a thrust toward the ball.
One number, no hiding
For a full swing we don't average the metrics — a plain average lets a serious fault hide behind everything you do well. The method is a weighted geometric mean, so the weakest link sets the tone. The whole-swing score is the one piece deliberately not shipped: the maths is written and the wrist score already runs on it, but a score is only as honest as the corridors underneath it, and the full-swing bands are still being seated on measured swings.
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Why averages mislead
Five perfect metrics (100) and one critical fault (20) average to a flattering 86 — a score that hides the very thing holding you back.
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The geometric-mean penalty
Multiplying the scores and taking the root lets one low number pull the whole score down. The same swing becomes a realistic 40.
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The coaching idea
You can't paper over a critical mechanical fault by perfecting something else. The score stays honest about what to fix first.
Illustrative — the same swing, two ways of scoring it.
There's no one right wrist
Unlike posture, wrist shape has no single correct answer — great players differ. So instead of scoring you against one ideal, we diagnose which style you're closest to.
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Three archetypes
Your wrist angles at the top and at impact are matched to three patterns: bowed (strong/closed), neutral, or cupped (open).
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A resemblance for each (0–100)
You get an independent match score for every archetype. Your highest one names your pattern; a high score means you're consistent within that style.
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Blended
If your top two scores are within 10 points, you're flagged "blended" — your wrist action is hybrid, and steadying onto one style is usually the goal.
Illustrative — resemblance scores name the swing's style.
A score with a margin
Cameras and sensors live in the real world — shadows, noise and timing jitter are facts of it. Rather than pretend to a false precision, the wrist resemblance score carries an honest range around it, propagated from a real error budget: sensor noise, the wrist cross-talk, and a timing term that grows when the phase ladder is poorly seated.
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"82 (±9)", not just "82"
The result is an interval — say 73 to 91, centred on 82 — that reflects the real margin of timing and sensor noise.
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Data quality sets the width
Good light, snug straps and two calibrated cameras give a tight band (±3). Poor light or loose straps widen it (±12).
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Noise never costs you
Lower confidence only widens the interval — it never lowers the score. A bad environment shouldn't dent your history. This replaced an earlier design in which confidence multiplied into the number itself — the surest route to being precise, confident and wrong.
Illustrative — the score sits inside an honest interval.
Fix one thing, then re-test
The point of all this measurement is a clear next move — not a wall of numbers. The aim is a simple, prioritised loop you can actually practise.
- 1
Know your style first
Check your wrist resemblance. If you're a bowed-wrist player, don't chase neutral or cupped tips — consistency within your own style is the goal.
- 2
Attack the top-ranked fault
Faults are ranked by points lost, so the top one is whatever is holding the score back most. Work on that single thing.
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Drill, then re-capture
Every ranked fault comes with a plain-English drill. Do it, capture a fresh swing, and watch that one metric drift the right way — and the interval tighten as it gets repeatable.
The takeaway: improvement isn't guesswork about "feel" — it's measured movement. Change one thing at a time, let the numbers confirm it, and trust the physics over the urge to overhaul everything at once.
Illustrative — the practice loop, one fault at a time.
Every metric, in plain terms
The walk-through above covered the ideas; this is the reference. The app's catalogue holds 95 metrics, and these are the ones worth knowing by name, grouped by what they tell you. Each is read at the swing's key positions (the P-position ladder, address to finish) and, where it is scored, held against a reference band at the phase that matters most.
A note on honesty: 52 of the 95 produce real output today — the wrist set, rotation, posture, the head, stance and balance, club delivery and tempo among them. Another 26 are readings a connected launch monitor supplies, and 17 are still to come: the depth-axis measures a face-on camera physically cannot see, and ball flight. The typical ranges are reference targets drawn from the published biomechanics literature and tour datasets, and stay provisional until our own validation completes. Each card flags what it needs:
Rotation & power — the engine
Pelvis rotation
pelvisRotationHow far the hips turn away from the ball and back through. The base of the coil and the first link in the sequence.
Thorax rotation
thoraxRotationShoulder turn — the larger of the two rotations, and the one that stretches the core against the hips.
X-factor
xFactorShoulders minus hips — the separation that stores elastic energy in the trunk. The single most-cited power measure in the literature.
X-factor stretch
xFactorStretchThe 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.
Shoulder plane angle
shoulderPlaneAngleHow 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.
Kinematic sequence
kinematicSequenceThe order and timing of peak rotational speed up the chain — hips, chest, lead arm, club. Out of order is the classic "casting" pattern.
Posture, tilt & the head
Secondary axis tilt
secondaryAxisTiltLean of the spine away from the target at impact — the hip-to-shoulder line measured from vertical in the face-on plane.
Spine side bend
spineSideBendShoulder line against hip line. Too little goes with a steep, over-the-top delivery; too much throws the low point behind the ball.
Head sway
headSwayLateral 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.
Head lift
headLiftRise 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.
Head tilt
headTiltChange in eye-line angle from address. Small and stable is normal; a large or abrupt change tends to accompany a loss of posture.
Spine forward bend
spineForwardBendHow 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.
Setup, stance & balance
These arrived with whole-body pose. The feet, heels and toes are landmarks in their own right now, which gives a ground line at shoe level rather than at the ankle — and with the ball in frame as a 42.67 mm ruler, several of them convert to real units.
Stance width
stanceWidthHeel-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.
Ball position
ballPositionWhere 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.
Foot flare
leadFootFlare / trailFootFlareHow 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.
Toe line
toeLineAngleStance 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.
Lead heel lift
leadHeelLiftHow 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.
Balance at the finish
comOverLeadFootHow 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.
Pelvis & lateral movement
Pelvis sway
pelvisSwaySide-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.
Pelvis lift
pelvisLiftThe 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.
Hip line tilt
hipLineTiltHow 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.
Plumb bob
plumbBobDistanceWhere 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.
Thorax lateral drift
thoraxLateralDriftThe 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.
Lead knee drift
leadKneeDriftThe 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.
Pelvis thrust
pelvisThrustMovement 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.
Lead wrist & forearm
Bow / cup
leadWristFlexExtFlexion (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.
Hinge (set / lag)
leadWristRadUlnRadial (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.
Forearm roll
forearmPronationAxial rotation of the lead forearm — the "roll" that squares the face through impact.
Forearm rotation from address
forearmRotationThe 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.
Lead elbow
leadArmFlexionHow straight the lead arm stays, from the shoulder, elbow and wrist geometry. A bent, lifting lead elbow late is the "chicken wing".
Measured twins
hm.leadWristFlexExt · hm.leadWristRadUln · hm.forearmRotationWhen 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.
Arms, connection & the trail side
Lead arm connection
leadUpperArmToChestThe 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.
Swing width at the top
leadHandWidthHow 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.
Trail elbow height
trailElbowHeightHow 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.
Lead arm to torso
leadArmToTorsoThe 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.
Trail wrist (the "tray")
trailWristFlexExtThe 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.
Elbow alignment
elbowAlignmentTrail 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.
Club delivery & speed
You might wonder why these sit here at all when a launch monitor already reads the ball and club. The overlap is deliberate. A launch monitor tells you the outcome; PinPoint tells you what the body did to cause it — and club delivery is where those two worlds meet. That's not hypothetical: a connected monitor's readings — over Open Connect or from a GCQuad — are recorded beside our own estimates on every swing, never replacing them. Where the shared numbers agree, each set vouches for the other: you get provenance for every reading, and a clean line from a fault in the ball flight back to the move that produced it.
Clubhead speed
clubheadSpeedSpeed 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.
Hand speed
handSpeedSpeed 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.
Lag angle
lagAngleThe 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.
Shaft lean
impactShaftLeanHow 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.
Shaft angle at the top
shaftAngleVsHorizontalSwing 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.
Attack angle
attackAngleWhether 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.
Low point
lowPointAheadHow 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 give you.
Transition plane delta
transitionPlaneDeltaWhether the club steepened or shallowed between backswing and downswing — over-the-top, quantified. Positive is steeper.
Club path
clubPathThe 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.
Swing plane
swingPlaneThe tilt and direction of the best-fit plane the clubhead travels on through the downswing — a genuinely three-dimensional object.
Ball flight & the launch monitor
The measured set
lm.… (26 readings)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 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.
Compound miss
compoundMissStart 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.
Ball speed & launch
ballSpeed · launchAngle · launchDirectionOur 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.
Tempo & the scores
Backswing time
tempoBackswingHow long the backswing takes, from address to the top — read straight from the swing's phase events, so it needs no particular device.
Tempo ratio
tempoRatioBackswing time divided by downswing time — the rhythm of the swing, and a number that's remarkably consistent among good players.
Wrist score
wristScoreThe 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.
Wrist resemblance
wristResemblanceHow 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".
Swing score
swingScoreThe 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.
Measured, not guessed.
Every method here is drawn from the published literature and held against real, hand-annotated swings before it ships. It's an open, inspectable platform — and still a prototype under validation: the first beta shipped in September 2026, with 1.0 targeted for late in the year.