Configure Context

To use this package, import it into your app together with the carp_mobile_sensing package:

import 'package:carp_core/carp_core.dart';
import 'package:carp_mobile_sensing/carp_mobile_sensing.dart';
import 'package:carp_context_package/carp_context_package.dart';

Before creating a study and running it, register this package in the SamplingPackageRegistry.

SamplingPackageRegistry().register(ContextSamplingPackage());

The context package uses different “services” (incl. the phone itself) to collect data.

Activity Measure

The ACTIVITY measure uses the phone itself and can be added like this:

// Create a study protocol
StudyProtocol protocol = StudyProtocol(
  ownerId: 'owner@dtu.dk',
  name: 'Context Sensing Example',
);

// Define the smartphone as the master device.
Smartphone phone = Smartphone();
protocol.addMasterDevice(phone);

// Add a background task that collects activity data from the phone
protocol.addTaskControl(
    ImmediateTrigger(),
    BackgroundTask(measures: [
      Measure(type: ContextSamplingPackage.ACTIVITY),
    ]),
    phone);

Each collected Activity holds the recognized ActivityType (IN_VEHICLE, ON_BICYCLE, ON_FOOT, RUNNING, STILL, or WALKING) and the confidence of the recognition in percent (0-100).

Since the activity recognition on both Android and iOS generates a lot of ‘useless’ events, the following events are discarded and never collected:

• UNKNOWN - when the activity cannot be recognized
• TILTING - when the phone is tilted (only on Android)
• activities recognized with a confidence below 50%

Location Measures

All of the location-based measures;

• LOCATION
• GEOFENCE
• MOBILITY

use the LocationService service as a “connected device” to collect data and can be added to a protocol like this:

// Define the online location service and add it as a 'connected device'
final locationService = LocationService(
    accuracy: GeolocationAccuracy.high,
    distance: 10,
    interval: const Duration(minutes: 1));

protocol.addConnectedDevice(locationService, phone);

// Add a background task that continuously collects location and mobility
// patterns. Delays sampling by 5 minutes.
protocol.addTaskControl(
    DelayedTrigger(delay: Duration(minutes: 5)),
    BackgroundTask(measures: [
      Measure(type: ContextSamplingPackage.LOCATION),
      Measure(type: ContextSamplingPackage.MOBILITY)
    ]),
    locationService);

Tip

You would often need to balance the configuration of the LocationService with the measure you are collecting. For example, if only using the MOBILITY measure, a lower accuracy, distance, and sampling interval could be used.

If you only want to collect location information one time during a measurement, you can override the sampling configuration using a LocationSamplingConfiguration like this:

// Add a background task that collects location on a regular basis
// using a periodic trigger and a location sampling configuration that only
// collects location data once.
protocol.addTaskControl(
    PeriodicTrigger(period: Duration(minutes: 5)),
    BackgroundTask(measures: [
      Measure(type: ContextSamplingPackage.LOCATION)
        ..overrideSamplingConfiguration =
            LocationSamplingConfiguration(once: true),
    ]),
    locationService);

Weather and Air Quality Measures

The WEATHER and AIR_QUALITY measure types use the online Open Weather API and Air Quality Open Data Platform, respectively. In order to use these services, you need to obtain an API key from each of them. Once you have this, these services can be configured and added to a protocol like this:

// Define the online weather service and add it as a 'device'
final weatherService = WeatherService(apiKey: 'OW_API_key_goes_here');
protocol.addConnectedDevice(weatherService, phone);

// Add a background task that collects weather every 30 minutes.
protocol.addTaskControl(
    PeriodicTrigger(period: Duration(minutes: 30)),
    BackgroundTask(measures: [
      Measure(type: ContextSamplingPackage.WEATHER),
    ]),
    weatherService);

// Define the online air quality service and add it as a 'device'
final airQualityService = AirQualityService(apiKey: 'WAQI_API_key_goes_here');
protocol.addConnectedDevice(airQualityService, phone);

// Add a background task that collects air quality every 30 minutes.
protocol.addTaskControl(
    PeriodicTrigger(period: Duration(minutes: 30)),
    BackgroundTask(measures: [
      Measure(type: ContextSamplingPackage.AIR_QUALITY),
    ]),
    airQualityService);

Note that the weather and air quality measures are so-called “one-time measures” and collect data once when triggered (in contrast to “event-based measures”).

See the example.dart file for more examples of how to set up a CAMS study protocol for this context sampling package.