One camera, and an honest account of what it can see.

Where the camera is standing

Down the line and face on are two different views of the same swing, and each hides what the other shows. A camera three metres behind you and waist high reads the swing plane reasonably and the shoulder turn badly. Move it square to your chest and the pair swap places. Almost nobody sets up on the exact line, so most real footage sits somewhere between the two, and the model has to guess how far.

What lens it used

Phones switch between wide, main and telephoto cameras without telling the application which one produced the frame, and each has a different distortion profile. A wide lens at two metres stretches whatever is nearest to it, which at address is usually your hands. Where the file records a focal length we use it. Where it does not, that is another band of uncertainty.

How the sensor reads out

Most phone sensors expose one row of pixels at a time from top to bottom rather than the whole frame at once. Anything moving fast enough leans over in the picture. A club at speed can appear bent, and a leaning shaft that was never leaning is exactly the kind of artefact that turns into a confident wrong reading if nobody accounts for it.

How many frames it captured

Thirty frames per second is the default on many devices and is not enough for the fast part of a golf swing. Sixty is better. One hundred and twenty is the point at which impact timing becomes solid. The application will read the actual frame rate from the file, tell you what that rate rules out, and offer to walk you through switching it before you record again.

Analysis runs on your phone by default

Pose estimation is designed to run inside the application on the device that recorded the clip. In that mode the video never leaves the phone, no frame is transmitted, and what the application keeps is a short list of numbers describing joint positions over time.

Uploading is a separate decision each time

Where a device cannot run the model, or where you ask a human to look at a swing, a recording has to be sent to a server. That is never automatic, never a background sync, and never the price of using the application. It is a per recording choice with the retention period shown on the same screen as the button.

Your swing does not become training data by default

No video, no frame and no derived pose sequence of yours is used to train or improve any model unless you have given separate, specific, revocable consent for that purpose. Consent to be analysed is not consent to be learned from, and bundling the two in one checkbox is the practice this paragraph exists to rule out.

No face recognition, no health inference

The application does not identify anyone by their face or their body, does not build a biometric template, and does not infer health, injury, disability, age, gender or any other characteristic about you. Faces are blurred on the device before any upload is offered.

Deletion means deletion

A recording can be deleted from inside the application at any time. Where a copy reached a server it is removed within seven days of the request and expires from backups on their ordinary rotation. We do not mark a record deleted and keep the file.