Android · optional phone recording
Phone motion & GPS
Record the hull with Sensor Logger while WitMotion records the oar. Upload both recordings together to add boat-motion curves, GPS and the inputs for boat replay.
1. Fix the phone to the boat
Use Sensor Logger by Kelvin Choi on Android. Mount the phone rigidly to the hull or a structure that moves with it, and keep it there for the whole recording. Its mounting angle can be arbitrary, but it must not shift.
A pocket, sliding seat or loose phone also records the rower’s or phone’s movement. That cannot be interpreted as hull motion.
2. Choose the phone sensors
Enable these streams before recording. Keep their original names and units.
| Sensor Logger stream | What it provides | Setting |
|---|---|---|
| Accelerometer | Linear acceleration for boat-motion analysis. | Enable |
| Gyroscope | Rotation of the phone and hull. | Enable |
| Orientation | Phone attitude needed for the default recorded-attitude analysis. Keep the standard quaternion export. | Enable |
| Location | GPS position, speed and route. | Enable |
| Gravity | Gravity direction for the boat reference. | Recommended when available |
| Total Acceleration | Acceleration including gravity, retained for boat-motion processing. | Recommended when available |
Request about 100 Hz for motion, or up to 200 Hz if supported. GPS can keep its own normal update rate, typically around once per second. Actual rates depend on the phone; do not repeat GPS fixes at the motion sampling rate.
3. Check that background recording works
- Allow recording access. Grant the motion, location and background permissions needed by Sensor Logger.
- Make a short trial. Start Sensor Logger, switch to WitMotion and record both sensors for a few minutes.
- Check both exports. Confirm Sensor Logger kept recording while WitMotion was in the foreground and that the two recordings overlap. If Android stopped the logger, review its battery restrictions and background-location settings, then repeat the trial.
4. Record the same workout
Start Sensor Logger shortly before the WitMotion workout recording. Keep WitMotion in the foreground throughout the row, then stop and save both recordings.
Use the phone’s correct date, time and timezone. The apps do not have to start at exactly the same instant. Avoid applying a separate clock correction in only one app.
5. Export separate sensor CSVs in one ZIP
- Choose Export → CSV in Zip File. Keep the separate sensor CSVs and Metadata.csv together, with their original filenames.
- Select the matching files for upload. In Cloud Analysis, choose Start new upload, then select the WitMotion workout TXT and Sensor Logger ZIP together. Include the short alignment TXT when you need a new oar alignment.
- Use one phone recording per workout. Do not mix different phones or multiple Sensor Logger sessions in the same upload.
Choose the separate-CSV ZIP export, not Combined CSV, JSON or SQLite. Combined CSV resamples the sensor streams. The separate files preserve the original motion and GPS timing.
You can also select the extracted CSVs, keeping their filenames, or place the WitMotion TXT beside an extracted Sensor Logger folder in one outer workout ZIP. There is no need to merge rows or convert files.
6. Review the recording timezone
Before running analysis, check Recording timezone matches the location of the row, for example America/Los_Angeles. The server can read this from Sensor Logger’s metadata; an explicitly selected setting takes precedence.
Sensor Logger records absolute timestamps, while WitMotion’s date/time text normally represents local time. A wrong timezone can put the recordings hours apart. Keep Metadata.csv and the original clocks; do not move the first rows into alignment by hand.
If the report has no overlapping phone data, check the timezone and that you selected the matching workout before changing other settings.
Continue in Cloud Analysis
After upload, review the settings and press Analyze workout. Phone motion adds boat curves and replay; location adds the route and GPS speed or pace. A Sensor Logger ZIP accompanies the oar workout TXT. Use Start new upload for another recording, or Re-analyze to change settings for the existing one.