Tap Zero on the Level tab while the phone rests on your reference plane. TrueLevel will then read tilt relative to that plane, so a known-flat surface shows 0.0°. Tap Reset zero to go back to absolute tilt.
Pitch is the tilt of the top edge toward or away from you; roll is the side-to-side tilt. Inclination is the total angle of the screen away from flat — 0° lying down, 90° on edge.
The Simulator provides only scripted motion. Use a physical iPhone or Apple Watch for real readings.
Accuracy depends on your device's motion sensors and how steadily the phone sits. For best results, let the phone settle, place it on a firm flat contact, and use the Zero function against a trusted reference. TrueLevel is a handy utility, not a calibrated laboratory instrument.
On your device, in SwiftData. Nothing is sent anywhere. Deleting the app removes everything, and you can clear the log any time from Settings.
Drop us an email with: iOS version, what you were measuring, and a short description of what you did and what happened. Screenshots help.