Mobile GPS Field Logger (Pro)

Turn your phone into a professional GPS tracking hub. The Logger is a dedicated app mode (?mode=logger) that does two jobs at once: it records your path while you're shooting, and it gives you a visible UTC time reference so you can align your camera's internal clock with the GPS track afterwards. That handshake is what we call the Sync Ritual.

flowchart TD
  A[Phone: open Logger] --> B[Photograph the<br/>UTC clock with camera]
  B --> C[Tap Initialize Tracking]
  C --> D[Shoot the rest of the day]
  D --> E[Tap Stop & Commit Track]
  E --> F{Transfer to desktop}
  F -->|Bridge code| G[Desktop pulls .gpx]
  F -->|Manual export| H[AirDrop / cloud / email]
  G --> I[Desktop: open Sync Photo<br/>read EXIF Date Taken]
  H --> I
  I --> J[Compute camera offset<br/>EXIF time vs UTC pixels]
  J --> K[Location tab → enter<br/>Time Offset]
  K --> L[Run Match]
  L --> M[Every photo gets GPS]

Opening the Logger on Your Phone

Getting the Logger onto your phone has two paths:

• Direct: open Jade GT in a browser on your phone and tap Mobile GPS Logger from the header. You're in.
• Desktop Bridge: if you're already at your desk, click Mobile GPS Logger on the desktop. Jade GT opens a pairing screen with a QR code you scan with your phone, plus a 6-character transfer code (displayed as ABC-DEF) for manual entry. Scanning the code loads the Logger URL on your phone directly.

The desktop Field Gear Bridge. Scan the QR on your phone to open the Logger, or enter the transfer code after recording to pull the finished .gpx back to the desktop app.

The Bridge screen is bidirectional: you use the QR code at the start of the session (desktop → phone), and the transfer code + Import flow at the end (phone → desktop) once your track is recorded.

The Sync Ritual Workflow

1. Grant geolocation permission when the browser asks. The Logger can't track your path without it.
2. Read the Temporal Calibration onboarding on first launch: a three-step walkthrough that explains why camera clocks drift and how the Sync Ritual corrects for it.

3. Photograph the UTC clock. The Logger displays a high-precision UTC clock; tap Fullscreen for a large, glare-free frame. Point your DSLR or mirrorless at the phone screen and take one photo of the clock. This single photo is your reference. It lets you compute the camera's offset later (see Computing Your Camera Offset).

   

   The fullscreen UTC clock: a photographable reference frame, not a feature that auto-detects the photo later.

4. Start tracking. Pick a Tracking Mode (see below), tap Initialize Tracking, and put the phone in your pocket. Keep the Logger tab open; mobile browsers stop background tracking if the tab is fully closed. Pause, resume, or discard the track at any time from the recording screen.

5. Transfer the track to the desktop. When you're done, tap the transfer button on the Logger's stopped-summary screen. You have two options:
   • Bridge transfer: back at your desk, open the Bridge modal (header → Mobile GPS Logger), enter the transfer code your phone shows, and click Import. The .gpx lands in the desktop app directly.
   • Manual export: tap Export GPX on the phone to save a plain .gpx file, then move it across with AirDrop, email, or a cloud drive, and drop it onto the Location tab in the desktop app.
6. Compute your camera offset and run the match. Covered in its own section below.

Sessions persist

Your in-progress track is saved to the browser's IndexedDB storage. If you accidentally reload the Logger tab, the recording is restored, not lost.

Recording Screen At-a-Glance

The Logger keeps every metric one glance away and the UTC clock always on screen.

While recording, the Logger shows:

• Duration and point count: time elapsed and fixes captured.
• Distance travelled: running total along the track.
• Current GPS accuracy (metres): lower is better.
• Live metrics: speed, elevation, bearing (where your phone reports them).
• Drop Pin: tag noteworthy spots with a named waypoint that ends up in the .gpx output.
• Optional satellite trail map: toggle on to see the path overlaid on imagery as you move.

Tracking Modes

Pick a mode before you hit record. Each trades battery life for point density:

Mode	Sample rate	Use when
Detail	1 second	Short, high-precision work (architecture, paparazzi)
Standard	5 seconds	Default for most day-long shoots
Battery	30 seconds	Multi-day hikes, wildlife, battery is the constraint

Two filters are always applied regardless of mode:

• 2-metre minimum spacing: consecutive points closer than ~2 m are dropped to avoid GPS noise clusters when you're standing still.
• 30-second stationary detection: if you stop moving, the Logger backs off from polling until it sees motion again, preserving battery.

Accuracy & battery

Position accuracy depends on your phone's GPS hardware; typical outdoor accuracy is 5 to 10 m. Continuous recording for several hours will meaningfully drain your battery. Battery mode plus a top-up before long shoots is the safe combination.

Computing Your Camera Offset

This is where the Sync Photo earns its keep. Don't skip it. An uncorrected 30-second clock drift puts every photo at the previous GPX point instead of where you actually pressed the shutter.

The idea in one sentence: the camera stamped its own (possibly wrong) time into the EXIF of your Sync Photo, while the pixels of that same photo show the correct UTC time from the Logger's clock. The difference is your camera's drift, and every other photo in the shoot carries the same drift.

Three moving parts to line up:

1. What the camera thinks the time was: visible in the EXIF Info tab as Date Taken when you open the Sync Photo in the desktop app.
2. What the time actually was: visible as pixels in the Sync Photo itself (the big UTC readout you photographed).
3. The offset: the difference between the two, entered into the Time Offset slider on the Location tab's GPX panel.

Worked example. You fly the Logger's clock at 21:02:43 UTC and press the shutter. Back at your desk, you open that photo and the EXIF says Date Taken: 14:02:17 (your camera was set to local, which for this shoot is UTC-7 → expected EXIF would be 14:02:43). So your camera clock is 26 seconds slow. Dial +26 s into the Time Offset slider. Done. Now click Run Match on the Location tab's GPX panel, and every photo in the shoot snaps to the closest GPX point within the match window.

If Match Preview says \"camera clock may be off\"

That warning appears when the majority of photos fall outside the match window, which almost always means your Time Offset is wrong. Click the Fix Clock button in the preview. It jumps you right back to the offset workflow.