Flying TeleMetrum with AltosUI on iPhone

TeleMetrum is Altus Metrum’s mainstay dual-deploy flight computer with GPS — capable and compact, and a great match for the AltosUI iOS app on launch day. This guide walks through what a TeleMetrum flight looks like on your iPhone, tab by tab, including an honest note on what TeleMetrum does not send so you aren’t left wondering why a field is missing.

What TeleMetrum reports

TeleMetrum (v1 through v4) reports a single-axis high-G accelerometer, a barometer, GPS, and two pyro channels. The accelerometer lets the flight computer sense boost directly, so state transitions come early and cleanly. What you will not see with TeleMetrum is 3-axis IMU tilt — that is TeleMega territory — and you will not see more than two pyro channels on the Pad tab. Those are hardware realities, not app limits.

For the full hardware specifics and firmware, the canonical source is altusmetrum.org/TeleMetrum.

On the Pad

The Pad tab is your readiness checklist. With a TeleMetrum at the other end you see whether the flight computer is armed, whether its two igniters — drogue and main — have continuity, whether the GPS has locked with enough satellites to be useful, the battery voltages for the rocket and the receiver, the flight computer’s firmware version, and the receiver’s own location.

Two-channel pyro continuity is the distinguishing Pad view for TeleMetrum: drogue and main, not six. Green across the board means the flight computer is ready to go.

Live on the Flight tab

Once the rocket leaves the rail, the Flight tab shows current flight state, current and maximum height, current and maximum speed, and the range, bearing, and elevation to the rocket relative to your position. Voice narration calls out the state transitions — pad, boost, coast, apogee, drogue, main, landed — and peak values as they happen. See the voice-callouts guide for the detail on what the app says when.

One honest note: the Flight tab also displays tilt during boost when the hardware reports it, and TeleMetrum’s single-axis accelerometer does not. If you want tilt readings off the pad, that is a TeleMega feature. TeleMetrum gives you altitude, velocity, and the state machine cleanly — which, for most dual-deploy flights, is what you actually want.

On the Map

Because TeleMetrum has a GPS, the Map tab plots the rocket’s full ground track over an Apple Maps basemap, with your position, the pad, and the rocket linked by lines. The map supports online Apple Maps or your pre-downloaded offline tiles, and the three standard map types — Road, Hybrid, and Satellite. If you enabled the Launch Site overlay in settings, the launch field appears as a shaded circle; the launch-site overlay feature page has the detail.

Walking to the rocket

With GPS on board, the Recover tab is fully featured for TeleMetrum. The default List mode shows bearing, direction, and distance from your position to the rocket’s last reported GPS fix, along with the rocket’s coordinates and the flight’s maximum values. The bottom mode selector switches to a dedicated walking map (Recovery Map) or the camera HUD (AR Recovery HUD) — both are covered in the AR recovery guide.

The AR HUD needs a rear camera, GPS location services, and an active telemetry connection to a GPS-equipped flight computer — and TeleMetrum qualifies. The dashed GPS Uncertainty Circle around the reported position shows how much ground “somewhere in here” actually covers, so you know how wide to search once you arrive.

IDLE mode and pre-flight igniter testing

IDLE mode is prep-area work, not pad-side work. At the prep table or trailer, with the receiver within radio range of the TeleMetrum, you can put the receiver into IDLE mode to query device state, set the callsign, read configuration, and run a continuity-protected igniter test with countdown guards. For TeleMetrum that’s a continuity check on drogue and main while the rocket is still at your prep area — before you carry it out to the pad. Once the airframe is at the pad and powered up vertical, the flight computer is in Pad mode, transmitting telemetry; your IDLE work is already done.

TeleMetrum’s two pyro channels each get their own continuity indicator during the IDLE test, mirroring the Pad tab view. Igniter firing is gated behind countdown guards so the test cannot go off by surprise.

Replay and post-flight review

After you’ve packed up, Flight Replay lets you play the recorded .telem file back through the full telemetry pipeline — the same Pad, Flight, Map, and Recover tabs that showed it live. Two timing modes cover the cases: Actual reproduces the original packet intervals so a 60-second flight takes 60 seconds, and Fast delivers packets at one-second intervals for a quick scan. Useful on TeleMetrum flights specifically for sanity-checking the boost-phase state timing against what you remember seeing.

Back at the car

AltosUI wrote a .telem file for the flight automatically — named by date, serial, flight number, and receiver, reachable through the Files app or iTunes Document Sharing. Tap it in Files and Quick Look gives you a summary card; Share to AltosUI generates the on-device Flight Report. See the telem-files guide and the Flight Report PDF guide for the hand-off path.

The launch-day checklist walks the full field workflow end to end. If you are coming to this page from outside the iOS ecosystem, AltosUI on iPhone: what it is (and what it isn’t) explains where the iOS app sits next to the desktop workbench.

One reminder on licensing

To legally operate an Altus Metrum flight computer in the US, you need at least a Technician-class amateur radio license. The canonical page is altusmetrum.org/Radio, and the ARRL licensing page is the place to start if you don’t already hold one.