Data types – Apple Watch Sensing

All measure types in this package live in the dk.carp.watch.aware namespace and are event-based: once started, they keep producing data until the study stops them.

Measure(type: AppleWatchSamplingPackage.MOTION)
// equivalent to
Measure(type: 'dk.carp.watch.aware.motion')

Constant	Type string	Data class
`AppleWatchSamplingPackage.MOTION`	`dk.carp.watch.aware.motion`	`AppleWatchMotion`
`AppleWatchSamplingPackage.HEART_RATE`	`dk.carp.watch.aware.heartrate`	`AppleWatchHeartRate`
`AppleWatchSamplingPackage.BATTERY`	`dk.carp.watch.aware.battery`	`AppleWatchBattery`
`AppleWatchSamplingPackage.LOCATION`	`dk.carp.watch.aware.location`	`AppleWatchLocation`
`AppleWatchSamplingPackage.HEADING`	`dk.carp.watch.aware.heading`	`AppleWatchHeading`
`AppleWatchSamplingPackage.BLUETOOTH`	`dk.carp.watch.aware.bluetooth`	`AppleWatchBluetooth`
`AppleWatchSamplingPackage.AMBIENT_NOISE`	`dk.carp.watch.aware.ambientnoise`	`AppleWatchAmbientNoise`
`AppleWatchSamplingPackage.AUDIO_LABEL`	`dk.carp.watch.aware.audiolabel`	`AppleWatchAudioLabel`
`AppleWatchSamplingPackage.DEVICE`	`dk.carp.watch.aware.device`	`AppleWatchDeviceInfo`

Common fields

All nine data classes extend AppleWatchData:

Field	Type	Meaning
`deviceId`	`String?`	The AWARE device id of the watch that collected the record
`timestamp`	`DateTime`	When the watch recorded it (UTC), not when the phone received it
`label`	`String?`	The AWARE data label from `AppleWatchDevice.label`, if set
`recordId`	`String?`	Stable identity of the record, used to discard duplicates

recordId is formed as watch device id / measure type / row id in the watch database. It makes re-transferred records safe: the same record never lands twice in the local CAMS database.

Reading the data

client.measurements
    .where((m) => m.dataType.toString() == AppleWatchSamplingPackage.HEART_RATE)
    .listen((measurement) {
      final heartRate = measurement.data as AppleWatchHeartRate;
      print('${heartRate.timestamp}: ${heartRate.hr} BPM');
    });

Data classes

Motion

AppleWatchMotion: sampled at motionSamplingRate Hz. Fields that belong to a disabled sub-sensor (accelerometerEnabled, deviceMotionEnabled) are zero.

Field	Unit	Description
`accX`, `accY`, `accZ`	G	Raw acceleration, including gravity
`roll`, `pitch`, `yaw`	radians	Attitude
`gravityX`, `gravityY`, `gravityZ`	G	Gravity vector
`rotationX`, `rotationY`, `rotationZ`	rad/s	Rotation rate
`userAccX`, `userAccY`, `userAccZ`	G	User acceleration, gravity removed

Heart rate

AppleWatchHeartRate: read from HealthKit on the watch.

Field	Unit	Description
`hr`	BPM	Heart rate in beats per minute

Requires the HealthKit capability and the participant's permission, granted on the watch. watchOS decides the sampling frequency, not this package: the watch measures more often during activity and less often at rest.

Battery

AppleWatchBattery: the battery of the watch itself.

Field	Unit	Description
`batteryLevel`	percent (0–100)	`-1` when unknown
`batteryState`	`WatchBatteryState`	`unknown`, `unplugged`, `charging`, or `full`

Note

watchOS reports the battery level in steps of 5%.

Location

AppleWatchLocation

Field	Unit	Description
`latitude`, `longitude`	decimal degrees	Position
`altitude`	meters	Above mean sea level
`ellipsoidalAltitude`	meters	Above the WGS 84 reference ellipsoid
`horizontalAccuracy`	meters	Radius of uncertainty
`verticalAccuracy`	meters	Vertical uncertainty
`speed`	m/s	Instantaneous speed
`speedAccuracy`	m/s	Accuracy of `speed`
`course`	degrees	Direction of travel relative to true north
`courseAccuracy`	degrees	Accuracy of `course`

Warning

If the phone also collects location through carp_context_package, disable one of the two. Otherwise you get two location streams.

Heading

AppleWatchHeading: compass and magnetometer.

Field	Unit	Description
`trueHeading`	degrees	Relative to true north
`magneticHeading`	degrees	Relative to magnetic north
`headingAccuracy`	degrees	Maximum deviation of the reported heading
`x`, `y`, `z`	microteslas	Geomagnetic field

Bluetooth

AppleWatchBluetooth: one record per device seen in a scan.

Field	Unit	Description
`identifier`	—	Identifier of the scanned device
`name`	—	Advertised name, if any
`rssi`	dBm	Received signal strength

Ambient noise

AppleWatchAmbientNoise: sound pressure level. No audio is stored.

Field	Unit	Description
`decibel`	dB	Sound pressure level

Requires audioEnabled: true together with ambientNoiseEnabled: true.

Audio label

AppleWatchAudioLabel: sound classification using Apple's SoundAnalysis. No audio is stored.

Field	Unit	Description
`audioLabel`	—	The classified sound, e.g. `speech` or `laughter`
`confidence`	0.0–1.0	Confidence of the classification

Requires audioEnabled: true together with audioClassificationEnabled: true. Filter on confidence in analysis: low-confidence labels are frequent in noisy environments.

Device information

AppleWatchDeviceInfo: collected once each time data collection starts on the watch.

Field	Description
`pairedIosDeviceId`	The AWARE device id of the phone this watch is paired with
`name`	The name of the watch, as set by the participant
`model`	Watch model, e.g. `Apple Watch`
`systemName`	Operating system name, e.g. `Watch OS`
`systemVersion`	Operating system version, e.g. `11.2`
`preferredContentSizeCategory`	The participant's dynamic type setting

This is the record that links the watch's AWARE device id to the phone's.