Barometer — tdlidar_barometer

Lift the phone a flight of stairs, or feel a door slam, through air-pressure changes.

Category: Motion · Tier: Free · Needs: any iPhone (no LiDAR required)

What it does

Streams two slow channels from the phone’s air-pressure sensor: a relative altitude in metres (how far up or down the phone has moved since the app started) and the raw pressure in kilopascals. It’s sensitive enough to register a single floor of a building, an elevator ride, or the pressure pop of a closing door. Updates arrive about once a second, so treat it as a gentle, ambient input.

OSC in

| address | type | range | rate | |—|—|—|—| | /tdlidar/motion/altitude/relative | float | metres (relative) | ~1 Hz | | /tdlidar/motion/altitude/pressure | float | kPa | ~1 Hz |

Outputs

out1 (CHOP) — 2 channels: relative (m) and pressure (kPa). The node tile previews out1.

Parameters

| par | default | what it does | |—|—|—| | OSC Port | 9000 | UDP port to listen on (match the app) |

Quick start (beginner)

  1. Enable Barometer in the app’s Motion sensors.
  2. Drop the Barometer op — two near-flat lines (don’t expect motion; it’s a quiet sensor).
  3. Carry the phone up some stairs: relative climbs by roughly +3 m per floor.
  4. Wire relative into a Range CHOP (e.g. 0–10 m → 0–1) and drive a vertical gradient or a particle-system height — literally “the higher you carry the phone, the higher the visual rises”.

Advanced patterns

  • Slow-input smoothing: At ~1 Hz the signal is steppy. A Filter CHOP (or Lag with a long lag) interpolates between samples so a height-driven parameter glides instead of jumping once a second.
  • Pressure-event trigger: Subtract a slow Lag copy of pressure from the live pressure to isolate sudden bumps (a door slam, an HVAC kick), then Trigger CHOP the difference.
  • Floor detection: Quantize relative with a Math CHOP (Divide by ~3, then Floor) into integer floor numbers and use a Switch TOP to change scene per floor for a multi-storey installation.
  • Combine with motion: Pair with Acceleration/Gravity so “moving up and accelerating” reads as an elevator vs walking.

Gotchas

  • Two channels, not three — this op breaks the X/Y/Z pattern of the other motion ops. Address relative and pressure by name.
  • ~1 Hz only. It is far slower than the ≤50 Hz motion sensors; never expect responsive, frame-rate control without a Filter CHOP to interpolate.
  • relative is relative to app launch (it starts near 0), not an absolute sea-level altitude. Restart the app to re-zero.