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Magnetometer

Live magnetic field readings for compass-related diagnostics, with combined and per-axis graphs.

Overview tab with compass visualization and live magnetic field readings

Overview​

The magnetometer measures the local magnetic field around the device. It is used for compass heading and can be affected by nearby metal objects or electronics.

Table of Contents​

Tabs​

  • Overview
  • Graphs (combined)
  • Graphs (per axis)

Toolbar Controls​

All motion-sensor tools share the same toolbar controls:

  • Play / Pause: start or pause sensor updates.
  • Clear: clear history buffers used by the graphs.
  • Refresh rate: cycle between Faster, Fast, and Slow sampling rates.

Overview Tab​

The Overview tab shows:

  • A detailed compass visualization with:
    • A stationary outer ring with cardinal (N, E, S, W) and intercardinal (NE, SE, SW, NW) direction markers. North is displayed in red.
    • Tick marks every 5 degrees, with three levels of prominence (30-degree marks tallest, 15-degree marks medium, 5-degree marks shortest).
    • A rotating inner compass rose that turns opposite to the heading direction.
    • A stationary triangle heading indicator at the top.
    • A field strength indicator at the center -- an XY-plane dot that moves based on X and Y field values, surrounded by a ring that scales with total field magnitude (capped at 100 uT).
  • Live values for magX, magY, magZ (in microtesla, uT).
  • A computed heading in degrees (calculated as atan2(y, x), converted to clockwise-from-north: 0 = North, 90 = East, 180 = South, 270 = West). Heading rotation is smoothed to avoid abrupt jumps.

Graphs Combined Tab​

Graphs (combined): X/Y/Z plotted together with an auto-scaled range

This tab overlays X/Y/Z history on a single graph (X = red, Y = green, Z = blue) and shows the current auto-scaled range. The Y-axis range is dynamically calculated based on the maximum absolute value across all readings, with 20% margin and a minimum of +/-100 uT. Current values use split-precision formatting. The graph retains up to 300 readings (larger than the 100 used by accelerometer and gyroscope).

Graphs Per Axis Tab​

Graphs (per axis): one panel per axis with independent ranges

This tab shows three separate panels (X, Y, Z), each with its own independently auto-scaled range and the current value displayed alongside the axis label.

What You Can See​

  • Magnetic field strength on the X/Y/Z axes (commonly in microtesla, uT)
  • Total field magnitude (if available)
  • Optional compass/heading view (if available)

Notes​

  • Readings are sensitive to interference (cases with magnets, speakers, laptops).
  • Compass accuracy can degrade indoors or near large metal structures.

Notes And Limitations​

  • Magnetometer availability varies by device and platform. On visionOS, the magnetometer is not available.
  • If readings look wrong, remove magnetic accessories and move away from large metal objects.
Last updated on by Rogerio Hirooka