User Guide

Everything about installing and jumping with AltiFenix. Questions: hello@altifenix.com.

What AltiFenix is

AltiFenix turns a Garmin watch into a glanceable barometric skydiving altimeter, modeled on the L&B Viso. It shows a large above-ground-level (AGL) altitude, zeroes itself automatically on the ground, and logs every jump hands-free (exit, deploy, freefall time, max vertical speed, canopy time). The altitude is barometric, with optional haptic altitude alerts. GPS is used only for the optional DZ-direction arrow and, when Share Diagnostics is on, the uploaded diagnostic track.

Installing the app (side-load)

Getting the app

You download AltiFenix yourself from this website:

1. Sign up at altifenix.com (name + email; tick the consent box for beta testing).
2. Open the personal link we email you. It takes you to a page that lets you download AltiFenix.PRG for your exact watch model – pick your model from the list and download it.
3. Install it over USB (below), then link the watch to your account with the pairing code (see Linking your watch).

Installing is one file: copy AltiFenix.PRG (the app you just downloaded) onto the watch over USB, into GARMIN/APPS/.

Optional (beta): also create an empty text file named AltiFenix.txt in GARMIN/APPS/LOGS/ (create LOGS if missing). It enables the on-watch diagnostic log – only useful if we ask you for logs when something goes wrong. Jump diagnostics otherwise upload on their own via Share Diagnostics.

Use a real USB data cable (not a charge-only one) and wake / unlock the watch so the computer can see its storage.

On macOS

macOS Finder doesn't handle Garmin's USB (MTP) reliably, so use OpenMTP (free): openmtp.ganeshrvel.com.

1. Install OpenMTP. The first time you connect the watch, macOS may ask for permission. If transfers fail or the watch never shows up, open System Settings → Privacy & Security → Accessories, find the watch, and set it to Always Allow.
2. Plug the watch in, then wait 10–15 seconds before opening OpenMTP. It often fails to connect if you open it too soon. If it does fail, quit OpenMTP, wait, and reopen it – that usually fixes it.
3. In OpenMTP, switch the device pane to the watch and open the GARMIN folder.
4. Copy AltiFenix.PRG into GARMIN/APPS/ (and, if you want the optional diagnostic log, an empty AltiFenix.txt into GARMIN/APPS/LOGS/).
5. Safely eject the watch. AltiFenix now appears in the watch's apps/activities list.

On Windows

Windows talks to the watch natively over USB (MTP) – no extra software is needed (and you do not use Garmin Express for this).

1. Plug the watch in and unlock it. It appears in File Explorer under This PC as a portable device named after your watch (e.g. fenix 8). If it shows up empty or not at all, give it a few seconds, then unplug/replug; if still empty, reboot the watch and try again.
2. Open the device → Internal Storage (or Primary) → GARMIN.
3. Copy AltiFenix.PRG into GARMIN\APPS\ (and, if you want the optional diagnostic log, an empty AltiFenix.txt into GARMIN\APPS\LOGS\, creating LOGS if missing).
4. Safely eject the watch. AltiFenix now appears in the watch's apps/activities list.

Linking your watch

The linking screen is the first thing you'll see when you open a freshly installed app on the ground. Your account (your name, and whether you're a beta tester) lives on the AltiFenix server, not in the app, so the build itself contains no names – linking the watch to your altifenix.com account is what puts your name on it:

• On first start, if the watch isn't linked yet and you're on the ground, AltiFenix opens a short linking screen showing a 6-character code (e.g. XK4 P2R) and altifenix.com/link. Enter that code on the link page (signed in via your personal email link) and, within a minute or two, About shows your name. Press BACK to skip the screen and go straight to the altimeter (it won't interrupt you again this session, and it never appears once you're airborne).
• Any time later, open Settings ▸ Link Watch to show the code again.
• No connection? The screen shows your short device code and a SELECT to retry hint instead. Link later from Settings once you're back online.
• To unlink, open Settings ▸ Unlink Watch and confirm. About drops your name and the linking screen returns on the next start.

Quick start

1. Install it (see Installing the app above).
2. Open the app. On the very first start you'll see the linking screen; after that (or one BACK) it's the Ground screen with a big altitude near 0.
3. Open Settings (tap the START button) and set:
   • Units – Meters or Feet.
   • Mode – Skydive or Wingsuit (sets jump-detection thresholds).
   • Next Jump # – type your real current jump number so the logbook counts onward from your actual total.
   • (optional) DZ Arrow / Compass, and Set DZ while standing in the landing area, if you want the direction-to-DZ arrow in the air (climb, freefall, and under canopy).
4. Before you trust it in the air, run Simulate Jump from the Debug menu (see Bench tools) to watch every screen on the bench, and do a ground test (walk up a hill or ride an elevator and watch the number track).

The screens

Ground screen

Shown whenever you're on the ground. It draws:

• Battery glyph at the top (green ≥ 40 %, amber 15–40 %, red < 15 %).
• Current time just below it.
• The big altitude number – live AGL, held at 0 on the ground (this 0 is the proof that auto-zeroing worked). With a DZ Offset active it instead reflects the offset, so it can read a negative number on the take-off ground (see DZ Offset).
• A stats line: Today N · <lifetime total> – jumps logged today, then your lifetime total.

From the Ground screen: DOWN opens the Logbook, UP opens the Info / currency card, START opens Settings.

In-air screen

Shown automatically once you're climbing, in freefall, or under canopy. It draws:

• Battery + time at the top.
• The big white altitude number (AGL), in the Viso number format (below).
• A small amber descent-rate line at the bottom: a triangle (▼ falling / ▲ climbing) plus the speed in m/s or ft/s. This figure is approximate – at ~1 Hz the descent rate under-reads and lags in freefall; treat it as a canopy aid.
• Lock padlock (amber, bottom-centre) whenever input is locked (see Input lock).
• An amber OFS … badge under the time whenever a DZ Offset is active.
• The screen is kept lit while you're in freefall and under canopy, so the number stays readable without waking it (the Bright Screen setting; “During Jump” by default).
• If Compass is on: a heading-up compass ring on the rim with a numeric bearing; North is red. If the magnetometer isn't calibrated it shows Calibrate instead of a ring.
• If DZ Arrow is on: an arrow pointing toward your saved DZ (in the climb, in freefall, and under canopy), with distance shown near the top, plus a small GPS satellite icon (grey = off, amber = acquiring, green = fix, red = denied). The arrow is amber while the fix or the saved DZ is rough and turns white once both are trustworthy. It draws on a rough (POOR) fix too – a coarse bearing home beats none. In the climb it points back toward the DZ you're climbing away from (a spotting aid), and with no DZ anchored yet it simply draws nothing.

The number format (L&B Viso style)

The altitude stays about 3–4 digits wide at any height by changing decimals with magnitude. The same rule applies to both units; the small m/ft sits to the lower-right of the number.

In meters a typical jump uses mostly whole numbers (exit ~4.00, canopy 1.00, pattern 300). In feet you'll see all three (exit 14.0, freefall 5.50, pattern 850).

Buttons & navigation

AltiFenix uses the 5 physical buttons (no touch). Behaviour depends on whether input is locked (below).

Input lock

To stop a button or wrist-knock from changing the screen or quitting the app mid-jump, AltiFenix locks input automatically while you're airborne (climb, freefall, canopy) and unlocks automatically after you land. While locked, an amber padlock shows at the bottom and navigation does nothing – except a triple-tap of START (three quick presses), which always unlocks so you're never trapped. A manual unlock is cleared at the next phase change, so AUTO behaviour resumes (e.g. it re-locks if you're still airborne, or stays unlocked once landed).

(A Simulate Jump locks exactly like a real jump – that's the point. Use the triple-tap START unlock to escape and cancel the sim, same as on a real jump.)

How auto-zeroing works

The altitude is AGL because the app zeroes itself to the drop-zone ground:

• When the watch is still on the ground for a short while, it sets the ground reference pressure – so the readout reads 0 at the DZ and corrects for the day's barometric drift before each load. It re-zeros to a new ground level once the pressure has settled – so moving to a different elevation (a different boarding spot, or riding up to a higher point) clears itself once you stop – while a slow lift-off creep, which keeps moving and never settles, is held so it can't quietly carry the zero up with you.
• The moment a jump ends (a confirmed landing) it snaps back to 0 at the landing pressure right away, instead of waiting for the next background pass – so if the reference drifted during the jump, it's corrected as soon as you're down.
• Once it detects climb / freefall / canopy, re-zeroing is locked out until a confirmed landing. It never re-zeros in the air.

If you forget to open the app before takeoff

AltiFenix runs a small background watcher about every 5 minutes while the app is closed. It does two things:

1. Tracks the ground pressure, so if you open the app mid-climb it can still seed a correct AGL zero instead of showing garbage.
2. Nudges you: when it sees you climbing a few hundred metres at aircraft rate it raises a “Climbing – open AltiFenix?” prompt. Open the app and the altitude will be correct for the rest of the jump.

So the two “forgot to open it” cases are both handled: respond to the prompt, or just open the app yourself during the climb.

Settings menu (START)

Grouped top to bottom: jump setup (Mode / Alerts / Next Jump #), display (Units / Bright Screen / Compass / Lock Screen), the Drop Zone submenu, then Link Watch, Share Diagnostics, and About last.

About screen: your name and your Unique ID

About has two identity pages, in order:

1. Identity (page 1): the app name and author, plus a “Beta tester” + your name credit once your watch is linked to your account. While unlinked it just shows the app identity.
2. Unique ID (page 2): your watch's full device ID as two lines of uppercase 4-character groups. This is the identifier your diagnostic uploads are keyed by.

Altitude alerts (vibration)

AltiFenix can buzz your wrist when you pass set altitudes during climb, freefall, and canopy. It's vibration only – nothing changes on screen – so it works the same on every watch and you can feel it without looking (handy when you can't read the screen at freefall speed). The number of buzzes tells you which alarm: more buzzes = lower / more urgent.

Alerts ship Off – this is a backup/awareness altimeter, not a primary, so it won't buzz unless you turn it on. Flip the master On in Settings ▸ Alerts to enable them; the slots below come pre-configured, so On is all it takes.

Defaults (each alarm is an altitude + a buzz count):

To change them: Settings ▸ Alerts → master On/Off, then Climb / Freefall / Canopy → pick a slot → set Altitude (typed in your active unit), Pulses (1–15), or Enabled.

Good to know:

• Alarms are phase-aware: a freefall alarm only fires in freefall, a canopy alarm only under canopy – so the 600 m freefall hard deck won't buzz when you're already under canopy at 600 m.
• Each alarm fires once per jump as you cross it.
• Buzzing uses the watch's vibration motor: it only works while AltiFenix is the open app (it is, during a jump) and obeys your watch's system vibration setting – if vibration is off on the watch, there's nothing to feel.

DZ Offset (take-off and landing at different elevations)

Normally AltiFenix zeroes itself to the ground it's sitting on, so the readout is 0 at the DZ. DZ Offset is for the case auto-zero can't see: you board at one elevation but land at another – a mountain DZ, a demo/exhibition jump, a cross-country.

1. Open Settings ▸ DZ Offset and type a signed value in your active unit: landing-area elevation − take-off elevation.
   • Landing area higher than where you board → a positive number (e.g. +300).
   • Landing area lower → a negative number (e.g. -300).
2. A confirmation previews the result – e.g. “Landing 0 / take-off −300 m” – before it takes effect. (Entering 0 turns the offset off.)

With an offset set, the readout shows 0 at the landing area and a negative number on the take-off ground (you really are below the landing area there). The offset also applies to the logged exit/deploy altitudes, so the logbook matches what you saw.

• While an offset is active, an amber OFS +300 m badge shows on every screen so you can't forget it.
• The offset clears itself at midnight (local time), so the next jump day starts clean – re-enter it if you need it again.
• Jump detection is unaffected: exit, deploy and landing are still detected normally.

Bright Screen

Bright Screen controls when AltiFenix turns the backlight up to full and keeps re-lighting it so the altitude stays readable without you waking the screen:

• Off – do nothing; the screen dims on the watch's normal timeout.
• During Jump (default) – lit through freefall and canopy; dark on the climb to save battery.
• In Air – lit through the climb, freefall and canopy.
• Always – lit the whole time AltiFenix is open.

You can re-lock the screen any time from Settings ▸ Lock Screen – useful if you triple-tapped to unlock it in the air and want it locked again.

Notes:

• It re-lights at full brightness; it cannot override your watch's own backlight timeout setting, so a longer timeout (Watch Settings) helps.
• On AMOLED watches the system enforces burn-in protection and may briefly refuse to hold the backlight – the app re-tries on its own, so you may see the screen dip and come back rather than stay perfectly constant.
• If you tap the top-left light button to turn the screen off in freefall, the app will light it back up within a second. Set Bright Screen to Off if you'd rather it leave the screen alone.
• It costs battery. If you're tight on charge, turn it off and the screen behaves normally (it'll dim on the usual timeout).

Logbook & currency

• Logbook (DOWN from Ground): a scrollable list of your recent jumps. Each record stores timestamp, exit altitude, deploy altitude, freefall time, max vertical speed, and canopy time. The watch keeps a rolling history of the most recent jumps; older summaries roll off, but your lifetime total never resets. Open a jump and, if a DZ was set, a DZ row shows the dropzone name (auto-matched from a built-in worldwide list of ~1,300 dropzones, or whatever you typed in DZ Name).
• Freefall graph: open a jump, then select Graph to see your freefall plotted on one gridded chart – altitude (cyan, left scale: m or ft) and descent rate (amber, right scale: km/h or mph) against time in seconds, with labelled axes and gridlines. The trace runs from exit to deploy (up to 5 minutes). It's kept for every jump while there's room in storage; if storage is full the jump still logs but has no Graph row. Older jumps logged before this feature, and any debug-generated jumps, won't have a graph.
  • Inspect exact values (scrubber): the graph opens as a clean overview; your first input reveals a cursor. Drag a finger along the plot (touch watches, e.g. fenix 8 AMOLED – the cursor follows your finger) or press UP / DOWN (any watch) to move it. A dot marks the cursor point on each line, thin lines drop to the axes, and the exact altitude (left), descent rate (right), and time (below) print in larger white numbers at those edges. The cursor snaps to real logged samples, so every value is the actual reading. BACK leaves the graph.
• Info / currency card (UP from Ground): Last jump date, Today, This year, and Total jumps.

The free trial

The logbook, currency card and freefall graph are the full-app features: they're free for your first 10 real jumps, after which opening the logbook or the currency card shows a short card (“Free trial used”) pointing you at altifenix.com. One BACK closes it and you're back on the altimeter. The altitude readout, alerts and auto-zeroing keep working as before.

A few details:

• Only real jumps count. The Simulate Jump and Random Jump(s) bench tools never use up the trial.
• It survives a reinstall. The count is tracked both on the watch and on the server (from your uploaded jumps), and the app uses whichever is higher – so reinstalling the app, or a season of airplane-mode jumps, won't hand you a fresh trial or wrongly lock you out.
• Beta testers are comped. If your watch is linked to a beta account, everything stays unlocked no matter your jump count – nothing changes for you.

Jump detection & modes

Exit, deployment and landing are detected automatically – there is nothing to start or stop. The two modes tune the detection to the jump type's descent speeds; pick the one that matches before you board:

Implausible “jumps” (bench tests, a fast elevator, an airliner cabin) are filtered out and never logged.

The big altitude number never depends on this detection – it is always live and correct. Detection only drives logging and the airborne zero-lockout, which are safe to be slightly late.

Known limitations

• Barometric, ~1 Hz. In freefall the number steps ~50 m per update and lags the sensor's internal filter.
• Descent rate is approximate, especially in freefall – it under-reads peak speed. It's most useful under canopy.
• Max speed is vertical only. A wingsuit's glide / horizontal speed is not captured.

Supported watches

AltiFenix is designed and built on a Garmin fenix 8 47mm, and beta testers have it working on several more models. It is built for the wider Garmin lineup that shares the hardware it needs (a barometric altimeter and the 5-button layout), but the remaining builds are untested on real hardware: there is no guarantee the app even launches. If you run it on one of these, please report how it goes – that's exactly the kind of feedback this beta is for.

Confirmed by beta testers: fenix 8 47mm · fenix 7 · fenix 7 Pro · fenix 7X · fenix 7X Pro.

Built for, but untested (your mileage may vary):

• fenix 8 – 43 mm, Pro 47 mm, Solar 47/51 mm
• fenix 7S (incl. Pro)
• fenix E
• epix (Gen 2) / epix Pro – 42 / 47 / 51 mm
• Enduro 3
• MARQ (Gen 2), incl. Aviator
• Descent Mk3 (43 / 51 mm) / Descent G2
• D2 Mach 1 / Mach 2 / Mach 2 Pro
• Instinct 3 AMOLED (45 / 50 mm) / Instinct Crossover AMOLED
• Forerunner 955 / 965 / 970

Touch-only and small-screen (under ~220 px) models are intentionally excluded – the button-based safety lock can't work on them.

Beta testing

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