phone magnetometer · raw vector field · walk and tap to sample · interpolated heat map of the invisible magnetic landscape · runs locally
your phone measures the magnetic field around it constantly. the field is not uniform. walls hide wiring. floors hide steel. devices have permanent magnets. walk around your space. tap a grid cell each time you stop. watch what your walls are hiding.
note: most browsers do not expose the raw magnetic field vector. this tool uses the device orientation (alpha/beta/gamma) as a proxy. on android with the magnetometer sensor enabled, the readings are direct. on ios, they are indirect but still respond to nearby magnetic anomalies. results are indicative, not scientific.
tip: open this on a phone, hold it level, and walk slowly. desktop browsers will not produce useful readings.