Configuring Background Data

Background data are collected by the participant's phone without any survey being open: location (GPS) and data from the phone's health platform.

Where background data are configured

Background data collection is set up once per study, in the Study Builder under Protocol → Background Data. The tab contains two cards: Location (GPS) and Health Data (Apple Health / Health Connect). Each card has its own switch.

Passive data collection means that the phone records data without the participant doing anything, in contrast to active data such as survey answers. Location is recorded in the background, also when the SMAAT app is closed. Health data are read from Apple Health (iOS) or Health Connect (Android) once a day by a background task.

Survey-time sensors are configured elsewhere. Motion sensors (accelerometer, gyroscope and others), location and health data can also be recorded only while a participant answers a particular survey. Those settings are in each survey's Sensors tab, described in Designing Surveys.

Study Builder, Protocol tab with the Background Data sub-tab open. The Location (GPS) card is switched on with the Sampling Rate set to Custom and the Custom GPS Options fields expanded. The Health Data card is shown below. — Protocol → Background Data with the Location (GPS) card set to Custom… and the Custom GPS Options open, followed by the Health Data card.

Location and health data as a video

A narrated walkthrough (3:57) in the study from the quickstart video: the Location card and its sampling rates, the settings of a preset and how to customize them, Health Data and its eight types, sensors during a survey, the Preview's Permissions view, and where the files appear. It is filmed in SMAAT on the Free plan. The narration is a synthetic voice; turn on captions in the player to read along.

Recorded in October 2026. Screens in newer versions of SMAAT may differ slightly. Chapters, transcript and all video tutorials →

Location (GPS)

Turning on Location (GPS) records the participant's geographic coordinates (latitude and longitude) in the background. The phone requires background location permission for this, which the SMAAT app requests when the participant joins the study.

Sampling rate presets

The Sampling Rate: menu offers three presets and a custom option. The presets differ in the positioning accuracy requested from the phone and in the minimum distance the phone must move before a new location is recorded. They do not set a time interval.

Preset	Requested accuracy	Minimum distance between records
Low (Battery Saving)	Low (roughly 1 km)	100 m
Medium (Balanced) (default)	Balanced (roughly 100 m)	50 m
High (Data Quality)	Best (highest accuracy the device offers)	1 m

All three presets also use the iOS activity type “Fitness”, let iOS pause updates automatically, and show the background location indicator on iOS. On Android the presets show a persistent notification titled “Location tracking active” with the text “Tracking your location in the background”.

Because a new location is recorded only after the phone has moved the minimum distance, a participant who stays in one place produces few location records at any setting. Higher accuracy and smaller distances use more battery.

Below the menu, Settings of this preset lists every value the chosen preset sends to the phone, named as in the Custom GPS Options. Customize these settings switches to Custom… with those values filled in, as a starting point for changes.

Custom GPS options

Choosing Custom… opens Custom GPS Options:. The fields are passed to the phone's location service (Expo Location) and fall into five groups:

Activity Type (iOS only): Other, Automotive Navigation, Fitness, Other Navigation or Airborne. The activity type tells iOS what kind of movement is tracked, so that it can optimise location updates.
Deferred updates: Deferred Updates Distance: (metres the device must move before an update), Deferred Updates Interval: (milliseconds between updates) and Deferred Updates Timeout: (maximum milliseconds to wait for an update).
Foreground service (the persistent notification Android shows while location runs in the background): Notification Title:, Notification Body:, Notification Color: (hex, for example #FF0000) and Kill on Destroy, which stops the service when the app is killed.
Location options: Accuracy: (Lowest, Low, Balanced, High, Best, Best For Navigation), Time Interval: (minimum milliseconds between updates), Distance Interval: (minimum metres between updates) and Timeout: (maximum milliseconds to wait for an update).
iOS options: Pauses Updates Automatically (iOS may pause updates, for example in a tunnel) and Shows Background Location Indicator (the blue status-bar indicator while location runs in the background).

Example: A commuting study that needs one location roughly every minute while participants travel could use Custom with Accuracy: Balanced, Distance Interval: 50 and Time Interval: 60000. The time interval is applied by Android; on iOS updates are driven by distance.

Troubleshooting: If a participant has no location records, check that background location permission was granted (“Always” on iOS, “Allow all the time” on Android) and that the phone's battery optimisation does not stop the app. Location records are stored on the phone and uploaded in batches, either by a background task that the operating system runs about once a day or when the participant starts an upload in the app, so new data can reach the dashboard with a delay.

Health Data (Apple Health / Health Connect)

The Health Data card reads health metrics that are already stored on the phone: in Apple Health on iOS and in Health Connect on Android. SMAAT does not measure these metrics itself. What is available therefore depends on the participant's phone and on any smartwatch or fitness band that writes to the health platform. Turn on the card's switch and tick the data types to collect under Data types to collect:. If no type is ticked, the card shows “Select at least one data type to collect.”

Permission required: Participants grant health-data access in the SMAAT app. On iOS, access is granted per data type in Apple Health; on Android, on the Health Connect permission screen. Data types that the participant declines are not collected, even if they are selected for the study.

Data types

Eight data types are available. Four of them carry a Wearable required badge: these are usually recorded only when the participant wears a paired smartwatch or fitness band, and a phone on its own yields no data for them.

Data type	What is read	Wearable required
Steps	Daily step count, aggregated per calendar day.	No
Resting Heart Rate	Individual resting heart-rate measurements in beats per minute.	Yes
Sleep	Sleep stage segments (light, deep, REM, awake) with their duration.	No
Active Energy	Active calories burned, aggregated per day (kcal).	No
Walking + Running Distance	Distance walked or run, aggregated per day (metres).	No
Blood Oxygen (SpO₂)	Blood-oxygen saturation samples (%).	Yes
Respiratory Rate	Breaths-per-minute samples.	Yes
Heart Rate Variability	Heart rate variability samples in milliseconds.	Yes

Heart rate variability differs by platform. iOS reports SDNN (the standard deviation of the intervals between heartbeats) and Android reports RMSSD (the root mean square of successive differences between those intervals). The two indices are not directly comparable. The unit stored with each value records which index was measured, so analyses can separate or model the two.

The Health Data card on the Background Data tab, switched on, listing all eight data types with checkboxes. Resting Heart Rate, Blood Oxygen, Respiratory Rate and Heart Rate Variability carry a Wearable required badge, and Heart Rate Variability shows the SDNN versus RMSSD note. — The Health Data card with all eight data types. Four types are marked Wearable required.

How health data are collected

Once per day: A background task reads the selected types at most once every 24 hours. The operating system decides the exact time.
Time window: The first run covers the previous 24 hours. Each later run covers the time since the last successful run, so days are not counted twice.
Missing permission: If health access has not been granted, the run is skipped and the window is not advanced, so the data are read once permission is given.
Upload: Each data type is uploaded as a separate sensor record. Types without any data for the period are not uploaded.

Troubleshooting: If health data are missing, confirm that the participant granted health access and that the phone actually holds the requested data. Health metrics are special-category data under GDPR Art. 9, so the consent form needs to cover them.

Where background data appear

Background location and health records are listed on the study's Sensors page (study dashboard → Sensors), where they can be filtered by participant and by sensor type. Each health data type appears as its own sensor type. Viewing and downloading these records is described in Background Sensor Data.

Next Steps

Related sections:

Designing SurveysBuild surveys and set survey-time sensors.Background Sensor DataView and download location and health records.Participant ManagementEnrolment, consent and prescreening.SettingsStudy status, encryption and deletion.Data OverviewReview and export survey responses.Frequently Asked QuestionsAnswers to common questions about SMAAT.