Laser TrueAxis ReferenceZero is designed to be used in landscape orientation only.
ZERO NOT VERIFIED · DO NOT USE READING
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Enter a target angle to compare
Waiting for sensor…
Measured axis only:phone top-to-bottom.
Keep the handset’s physical top-to-bottom axis aligned with the slope. The number comes from the long-axis gravity component only. The phone must stay on its THIN EDGE. Rolling onto its flat back invalidates ZERO and hides the reading. At very steep angles (approximately 77° and above), gravity cannot reliably distinguish the contact face, so the app hides the measurement. A camera bump or case can also affect physical contact.
ZERO measures the change from your starting position. Align the phone’s long axis with the slope, press ZERO, and hold still for roughly two seconds. The app checks raw gravity readings for motion, trims outliers and averages them. Enter a target angle in the right panel; the comparison shows displayed reading minus target. A negative difference means below the target, positive means above it. The target does not change ZERO, calibration or the sensor calculation. CALIBRATE LEVEL is only for a genuinely known-level reference, not an arbitrary starting angle. RESET ZERO clears the saved reference. The display remains UNVERIFIED until a fresh ZERO succeeds in this session. If ZERO fails, the target highlight stays disabled; a green reading means a stable target match, not certified accuracy. Some browsers cannot report which landscape direction is in use: if you rotate the phone 180°, press ZERO again even if the browser does not detect it. Display resolution is 0.1°; phone-to-phone accuracy is unverified.
This tool needs gravity-inclusive motion sensor access to measure one physical axis. Open the HTTPS link directly in Safari or Chrome.