useAltimeter

Derived from the physical air pressure sensor via expo-sensors. Computes altitude above calibrated sea level using the standard barometric formula: h = 44330 * (1 - (P / P0)^0.1903). Automatically computes vertical velocity (rate of climb/descent in m/s) with exponential smoothing, categorizes atmospheric pressure trends (rising, steady, falling, rapid_fall), and supports local QNH calibration.

Signature

useAltimeter(updateIntervalMs?: number): AltimeterTelemetry

Inputs

Parameter	Type	Description
`updateIntervalMs`	`number`	Sampling period in milliseconds for the barometer, defaulting to 100ms.

Outputs

Field	Type	Description
`altitudeM`	`number \| null`	Current barometric altitude in meters above calibrated sea level. Null until first sample.
`altitudeFt`	`number \| null`	Current barometric altitude in feet above calibrated sea level. Null until first sample.
`verticalVelocityMs`	`number \| null`	Rate of climb or descent in meters per second (m/s), smoothed over recent samples. Null until moving.
`pressureHpa`	`number \| null`	Raw atmospheric pressure in hectopascals (hPa / mbar).
`seaLevelPressureHpa`	`number`	Calibrated reference sea-level pressure in hPa. Defaults to standard 1013.25.
`pressureTrend`	`'rising' \| 'steady' \| 'falling' \| 'rapid_fall' \| null`	Short-term pressure change trend indicating weather changes (rapid_fall indicates storm front).
`isAvailable`	`boolean`	Whether the hardware barometer is present and streaming.
`error`	`string \| null`	Error message if sensor access or subscription failed.
`source`	`TelemetrySource`	Data provenance: ‘derived’ from hardware barometer, or ‘unavailable’.
`calibrateSeaLevel`	`(hPa: number) => void`	Calibrates reference sea-level pressure (QNH) to zero out local elevation.
`resetCalibration`	`() => void`	Resets sea-level reference pressure back to standard 1013.25 hPa.

Functions

Function	Inputs	Returns	Description
`calibrateSeaLevel(hPa)`	none	`void`	Sets the baseline sea-level pressure (QNH) in hPa.
`resetCalibration()`	none	`void`	Resets sea-level pressure back to standard atmosphere (1013.25 hPa).

Example

import { useAltimeter } from '@pixelkit-labs/sdk';

function AltimeterHUD() {
  const { altitudeM, verticalVelocityMs, pressureTrend } = useAltimeter(100);
  return <Text>Alt: {altitudeM?.toFixed(1) ?? '—'} m · VSI: {verticalVelocityMs ?? '—'} m/s · Trend: {pressureTrend ?? '—'}</Text>;
}