Tracking with TeleGPS and AltosUI on iPhone

TeleGPS is the Altus Metrum answer to “I want a GPS beacon in this airframe, but I’m not flying an Altus Metrum deploy computer.” It is a tracker, not a dual-deploy flight computer, and AltosUI on iPhone treats it accordingly — with a simpler flight view and a recover view that is really the main event. This guide walks what you see and what TeleGPS is good for.

What TeleGPS is

TeleGPS (v1 through v4) is a tracker-only device. It has GPS and a simplified flight state machine: pad → flying → landed. There is no accelerometer on board, so the state machine cannot sense boost or apogee directly the way TeleMetrum or TeleMega can. What TeleGPS does well is one thing — report its position over the Altus Metrum radio link so you can find it after landing.

Think of TeleGPS as “bring a GPS beacon to any airframe.” You can fly it alongside a non-Altus-Metrum deploy system, in a payload bay on a dual-deploy build to add a second independent location source, or in a simple single-deploy sport flight where the only thing you really want is a recovery position. The canonical hardware reference is altusmetrum.org/TeleGPS.

On the Pad

The Pad tab with TeleGPS shows the tracker’s battery voltage, its GPS-lock status, the number of satellites, firmware version, and the receiver’s own battery and location. There are no pyro channels to check because TeleGPS has no pyro channels — it doesn’t fire anything; it just reports where it is.

The thing to watch for here is the GPS lock. TeleGPS’s entire job is delivering a position, so a healthy fix with enough satellites before launch is the readiness bar.

Live on the Flight tab

Because TeleGPS uses a simplified state machine, the Flight tab shows a reduced set of fields during flight: GPS fix status, altitude, and speed derived from GPS, plus the range, bearing, and elevation from your position to the tracker. What you will not see with TeleGPS are the fields driven by accelerometer data — no tilt during boost, no accelerometer-derived peak acceleration, no fine-grained boost or coast state transitions.

Voice narration still runs, but it rides on the simpler state machine — “pad,” “flying,” “landed” instead of the full boost / coast / drogue / main arc that accelerometer-equipped flight computers produce. Direction-aware speed callouts work as designed: “ascending at N m/s” during the ascending portion of “flying,” “descending at N m/s” during the descent. See the voice-callouts guide for the detail. This is expected behavior, not a missing feature — GPS-only hardware cannot sense motor events directly.

On the Map

TeleGPS has GPS, so the Map tab works the way it does on every other GPS-equipped flight computer: ground track over an Apple Maps basemap, with your position, the pad, and the tracker linked by lines. Online tiles or your pre-downloaded offline tiles, Road, Hybrid, or Satellite map types, and the Launch Site overlay if you have it enabled in settings.

Recover: the main event

The Recover tab is where TeleGPS earns its keep. The default List mode shows bearing, direction, and distance from your position to the tracker’s last reported GPS fix, along with the tracker’s coordinates. The Map mode is the dedicated Recovery Map walking view, and the AR mode is the AR Recovery HUD. Both work fully with TeleGPS because the HUD’s one hard requirement is an active telemetry connection to a GPS-equipped flight computer — and TeleGPS qualifies.

The dashed GPS Uncertainty Circle is drawn around the reported position in both modes, sized to the tracker’s reported HDOP. For a flight that landed under trees or behind terrain, the circle grows to reflect the weaker reception — exactly the information you want before you start searching. The AR recovery guide walks the walk-up.

Tracking alongside another rocket

TeleGPS earns extra utility at club launches where you have more than one rocket in the air over the course of the day. AltosUI keeps a list of the trackers you’ve seen, with per-tracker metadata that sorts by age, callsign, frequency, or serial number, and you switch between them one at a time as the flight order moves along. Dropping a TeleGPS into an otherwise non-Altus-Metrum airframe is a clean way to add one more entry to that list without rebuilding the deploy electronics.

IDLE mode on TeleGPS

IDLE mode is prep-area work, not pad-side work. At the trailer or prep table, with the receiver within radio range of the TeleGPS, you can put the receiver into IDLE mode to query device state, set the callsign, and read configuration. TeleGPS has no pyro channels, so there is no igniter test to run — but the configuration read is still useful to confirm the unit is set up the way you intended. Once you carry the airframe out to the pad and power up vertical, the flight computer wakes in Pad mode and transmits; IDLE work is done by then.

Replay and post-flight review

Flight Replay works with TeleGPS recordings just like it does for the rest of the lineup. Play the recorded .telem file back through the full telemetry pipeline in Actual timing or Fast timing. For TeleGPS, the Map and Recover tabs are the main attractions during replay — you can watch the ground track build up, review the walk-out to the landing site, and sanity-check the GPS accuracy through descent.

Back at the car

AltosUI still writes a .telem file for TeleGPS recordings, and you can still open one with Quick Look in the Files app and generate an on-device Flight Report. The report fills in what it can from GPS data — altitude profile, GPS track analysis, recovery performance — and labels fields that depend on missing sensors rather than showing unexplained dashes. See the telem-files guide and the Flight Report PDF guide for the hand-off.

For the full field workflow, the launch-day checklist is the hub. If you are new to the iOS app, AltosUI on iPhone: what it is (and what it isn’t) puts TeleGPS in context alongside the other Altus Metrum hardware.

One reminder on licensing

TeleGPS is a radio transmitter. To legally operate an Altus Metrum flight computer — including TeleGPS — 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.