GTrace - G-Meter & Logger

Track day or mountain road, every G you used stays on record.

GTrace turns your iPhone into a real G-meter. It draws the lateral and longitudinal G-forces from your cornering, braking and throttle as a live trace, then lets you replay the run against the map, your footage or the graphs. Record video with audio and create shareable videos with G-force traces and readings overlaid on your footage.

One-time purchase. No subscription, no in-app purchases.


WHILE YOU DRIVE

- Live G-G diagram, lateral and longitudinal G shown together
- Trailing trace, with peak lateral and longitudinal G held on screen
- Jerk shown as a crosshair, so you can see how smoothly you transfer load
- Speed readout, switchable between km/h and mph
- Audible alert when you exceed your chosen G threshold
- Comfort and Sport modes with separate display ranges for street and track
- Three display layouts: standard, info + speed, and video preview
- Phone holder mode, so a vertically mounted phone still reads longitudinal G correctly


MEASUREMENT

- Gravity component removed to isolate true vehicle acceleration
- 2nd-order Butterworth IIR low-pass filter with adjustable cutoff frequency
- Configurable sampling rate
- Axis inversion, so mounting orientation doesn't matter


AFTER THE RUN

- G-G heat map showing which part of the friction circle you actually used, so you can see the balance between cornering, braking and acceleration at a glance
- Synced playback: G-G + map, G-G + video, G-G + acceleration graph, or map + graph, at adjustable playback speed
- Time-series graphs for longitudinal G, lateral G, longitudinal jerk, lateral jerk and speed
- GPS trace drawn on a map, with top and average speed


RECORD AND SHARE

- Voice recording, synced to the acceleration data for commentary and notes
- Video recording with audio, played back with the G-G trace overlaid
- Shareable video export: overlay G-force traces and readings on recorded footage. Export the whole clip or a selected range.
- Select video recording resolution: 480p, 720p or 1080p
- CSV export for spreadsheets or your own analysis tools
- Native binary format (.ggx) import and export, for backups and moving data between devices


WHO IT'S FOR

- Track day, sports driving and time attack enthusiasts
- Drivers working on their technique on mountain roads
- Anyone chasing smoother, more passenger-friendly load transfer
- Motorsport competitors who want their practice data kept
- Anyone who wants their car's behaviour in numbers


English and Japanese. iPhone only, iOS 15.6 or later.

Note: measurements use the iPhone's built-in accelerometer and gyroscope. Mount the phone firmly in the vehicle for accurate readings.
Note: GPS trace and speed recording require location permission.
Note: this app does not include lap timing.