Measure types – Mobile Sensing

Measure types available in the built-in and external CAMS sampling packages, with platform availability.

This page lists the measure types available in sampling packages, both the packages built into the carp_mobile_sensing framework and the external ones. The list evolves as support for more measures is released.

Measure type format

The dataType property of a Measure specifies the type of data to collect. Its string form is typically a namespace plus a name. CAMS-native measure types use the namespace dk.cachet.carp, and the name is the measure type:

dk.cachet.carp.<type>

Legacy namespace

The cachet part of the namespace is a legacy. The original vision and design of CARP was done at the Copenhagen Center for Health Technology (CACHET), and the namespace dk.cachet.carp was adopted then. CACHET has since closed, and CARP is now maintained by the Section of Digital Health at the Department of Health Technology at the Technical University of Denmark.

The old namespace is kept for backward compatibility. It will be changed to carp.dk in the future.

Event-based and one-time measures

Kind	Behavior	Example
Event-based (EB)	Once triggered and started, continuously samples data from its sensor until explicitly stopped. Most measures are event-based.	A step event every time the phone detects a step.
One-time (OT)	Samples one piece of data when triggered.	Weather data from the Open Weather API.

The kind matters when you specify a study protocol: an event-based measure can be started and runs until stopped, whereas a one-time measure must be triggered to sample data. You can, for example, trigger it periodically with a PeriodicTrigger.

In this protocol, the first task contains a one-time measure (device information) that is triggered only once. The second task contains event-based measures that start immediately and keep sampling data based on events. The third task collects weather (a one-time measure) periodically every 5 minutes.

  // Collect device info only once, when this study is deployed.
  protocol.addTaskControl(
    OneTimeTrigger(),
    BackgroundTask(
        measures: [Measure(type: DeviceSamplingPackage.DEVICE_INFORMATION)]),
    phone,
  );

  // Immediately start collecting step count, ambient light, screen activity, and
  // battery level events. All event-based measures.
  protocol.addTaskControl(
    ImmediateTrigger(),
    BackgroundTask(measures: [
      Measure(type: SensorSamplingPackage.STEP_EVENT),
      Measure(type: SensorSamplingPackage.AMBIENT_LIGHT),
      Measure(type: DeviceSamplingPackage.SCREEN_EVENT),
      Measure(type: DeviceSamplingPackage.BATTERY_STATE),
    ]),
    phone,
  );

  // Add a background task that collects weather every 5 minutes.
  protocol.addTaskControl(
      PeriodicTrigger(period: Duration(minutes: 5)),
      BackgroundTask(
          measures: [Measure(type: ContextSamplingPackage.WEATHER)]),
      weatherService);

Each SamplingPackage lists the measure types it supports in its dataTypes property, and provides a default sampling schema for each of its measure types.

Available measure types

CAMS has a large set of predefined measure types, each available in a sampling package. Some measures are part of CAMS, others are available in separate sampling packages, and some are part of device-specific sampling packages.

For each measure, the tables list:

Type: all type names have the format dk.cachet.carp.<type>, where type is listed in the table.
Android and iOS: availability on each platform.
Package: the sampling package that contains the measure.
Description.

Types marked with * are one-time measures.

Built-in sampling packages

Type	Android	iOS	Package	Description
`acceleration`	Yes	Yes	sensors	Rate of change in velocity in x, y, z, including gravity
`nongravitational acceleration`	Yes	Yes	sensors	Rate of change in velocity in x, y, z, excluding gravity
`acceleration features`	Yes	Yes	sensors	Acceleration events over a specific sampling period, with calculated higher-order features
`rotation`	Yes	Yes	sensors	Rotation of the device in x, y, z (typically measured by a gyroscope)
`magneticfield`	Yes	Yes	sensors	Magnetic field around the device in x, y, z (typically measured by a magnetometer)
`stepevent`	Yes	Yes	sensors	Step events from the device's onboard sensor
`ambientlight`	Yes	No	sensors	Ambient light from the phone's front light sensor
`deviceinformation`*	Yes	Yes	device	Basic device information
`application information`*	Yes	Yes	device	Information about the app
`batterystate`	Yes	Yes	device	Battery charging status and battery level
`screenevent`	Yes	No	device	Screen events (on/off/unlock)
`applifecycleevent`	Yes	Yes	device	App lifecycle state events (inactive, hidden, paused, resumed, detached)
`freememory`	Yes	No	device	Free memory
`timezone`*	Yes	Yes	device	Timezone of the device
`heartbeat`	Yes	Yes	device	A heartbeat measurement every 15 minutes (default) telling whether the app is running (and not killed by the OS)

External sampling packages

Type	Android	iOS	Package	Description
`location`	Yes	Yes	`context`	Listens to the stream of location changes from the phone's OS
`activity`	Yes	Yes	`context`	Activity as events from the OS's built-in activity recognition API
`weather`*	Yes	Yes	`context`	Detailed weather information for the current location of the phone
`airquality`*	Yes	Yes	`context`	Air quality of the current location of the phone (from land-based stations)
`geofence`	Yes	Yes	`context`	Tracks entry, dwell and exit events in circular geofences
`mobility`	Yes	Yes	`context`	Tracks location and calculates mobility features based on the `mobility_features` plugin
`bluetooth`	Yes	Yes	`connectivity`	Scans nearby BLE devices
`wifi`	Yes	No	`connectivity`	Collects SSID and BSSID from connected Wi-Fi networks
`connectivity`	Yes	Yes	`connectivity`	Connectivity status events
`beacon`	Yes	Yes	`connectivity`	Scans for nearby iBeacons
`audio`*	Yes	Yes	`audio`	Records audio from the device microphone
`noise`	Yes	Yes	`audio`	Detects ambient noise from the device microphone
`apps`*	Yes	No	`apps`	List of installed apps
`appusage`*	Yes	No	`apps`	List of app usage
`phonelog`*	Yes	No	`communication`	Log of incoming and outgoing phone calls
`textmessagelog`*	Yes	No	`communication`	Log of incoming and outgoing text messages (SMS)
`textmessage`	Yes	No	`communication`	Text message (SMS) events when received
`calendar`*	Yes	Yes	`communication`	Calendar events from the calendars on the phone
`survey`*	Yes	Yes	`survey`	Data from surveys (questionnaires) through the Research Package, and cognitive assessments from the Cognition Package

Wearable device sampling packages

Type	Android	iOS	Package	Description
`health`	Yes	Yes	`health`	Different types of health data from Apple Health and Google Health Connect, which may come from connected wearable devices
`movisens`	Yes	No	`movisens`	Activity and heart rate monitoring using the Movisens Move4 and EcgMove4 devices
`esense`	Yes	Yes	`esense`	Inertial measurement unit (IMU) sensor events and button press/release events from the eSense device
`polar`	Yes	Yes	`polar`	Inertial measurement (accelerometer, gyroscope, magnetometer) and heart rate (ECG, PPI, PPG, HR) data from Polar devices
`movesense`	Yes	Yes	`movesense`	State (tap), heart rate (HR), ECG and inertial measurement unit (IMU: accelerometer, gyroscope, magnetometer) data from Movesense devices
`watch.aware`	No	Yes	`aware`	Motion, heart rate, battery, location, heading, Bluetooth, ambient noise and sound classification collected on an Apple Watch using the AWARE watchOS framework. These measures use the `dk.carp.watch.aware` namespace; see Apple Watch Sensing.

Each of these device measures has sub-types, such as dk.cachet.carp.movisens.hr for heart rate (HR) measures from the Movisens device.