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Sensor Usage

This page covers how sensor data is collected, quality monitoring, and troubleshooting.

Two Types of Data​

Background (Passive) Data​

Collected automatically by the device without participant action. Includes GPS location, accelerometer readings, device state, step counts, and health platform data. Runs continuously when the app is installed and permissions are granted.

Participant-Generated (Active) Data​

Collected through direct participant interaction — survey responses, cognitive game scores, journal entries, voice recordings. Active data is produced when participants complete activities.

Data Collection Workflow​

  1. Configuration — Researchers configure which sensors are active through the Sensors tab.
  2. Permissions — Participants grant device permissions during setup (see Download & Setup).
  3. Collection — The app collects sensor data in the background continuously.
  4. Caching — Data is stored locally on the device, enabling offline collection.
  5. Sync — Data is transmitted to the mindLAMP server when a network connection is available.
  6. Privacy — Data is transmitted securely. Access is controlled through the API's credential system.

Background Collection​

For details on how background collection works, offline behavior, and battery considerations, see Background Collection.

Data Quality Monitoring​

Dashboard Indicators​

The Users tab in the dashboard shows color-coded data quality indicators for each participant (green, yellow, red, gray) based on how recently passive data was collected. See Users Tab — Data Collection Status for the full threshold definitions.

Cortex Data Quality Metrics​

The Cortex library provides quantitative data quality features:

data_quality — Measures data availability as a percentage within configurable time bins. Specify the sensor and bin_size in milliseconds to compute the fraction of each bin containing at least one data point.

import cortex

result = cortex.run(
    "U1234567890",
    features=["data_quality"],
    feature_params={
        "data_quality": {
            "feature": "gps",
            "bin_size": 3600000  # 1-hour bins
        }
    },
    start=start_time,
    end=end_time
)

How Data Quality Is Calculated​

The Cortex data_quality feature divides a time window into fixed-size bins and measures the proportion of bins that contain at least one data point. It supports two sensors, each with a different default bin size:

SensorDefault bin size
GPS10 minutes (600,000 ms)
Accelerometer1 second (1,000 ms)

The bin_size parameter can be overridden to any value in milliseconds. A score of 1.0 means every bin had data; 0.0 means none did.

Key Factors Affecting Data Quality​

  • App interaction frequency — Passive data quality is strongly correlated with active data quality (Spearman's r = 0.94; Calvert et al., 2026). Modern operating systems (iOS 15+, Android 12+) restrict background processes for apps not regularly used. Daily app interaction — such as completing a survey — helps keep the app in active status and prevents OS suspension of background data collection.
  • Data quality degrades within ~3 days without app interaction, as background processes are progressively throttled by the operating system (Currey & Torous, 2023).
  • Low Power Mode is the most common resolvable cause of poor data quality (Calvert et al., 2026).

Troubleshooting​

Quick Check

Before investigating data quality issues:

  1. Permissions — Verify all required permissions are granted (Location "Always", Motion & Fitness, Health data).
  2. Battery optimization — Confirm mindLAMP is exempt from battery saver / Low Power Mode.
  3. App status — Check that the app has not been force-quit or uninstalled.
  4. Connectivity — Ensure the device has WiFi or cellular data for syncing.

Common Causes​

IssueLikely CauseSolution
No data at allPermissions not grantedCheck Download & Setup
Intermittent gapsApp force-quit or battery optimizationEnsure mindLAMP is exempt from battery optimization
Reduced frequencyLow Power Mode activeDisable Low Power / Battery Saver
Data stops after a few daysOS restricted background processesFollow device-specific guidance at dontkillmyapp.com

iOS​

  • Are all relevant permissions granted for mindLAMP 2 in the Settings app?
  • Is Low Power Mode turned off?
  • Is Airplane Mode turned off?
  • Is the device connected to WiFi or cellular data?
  • Is the device powered on at all times?
  • Has the app been force-quit by swiping it away?

Android​

  • Is Battery Saver mode disabled (including automatic schedules)?
  • Is Airplane Mode turned off?
  • Are all relevant permissions granted?
  • Is the device connected to WiFi or cellular data?

Some Android manufacturers aggressively restrict background processes. For Samsung, OnePlus, Huawei, and Xiaomi devices, visit Don't Kill My App for device-specific recommendations.

Battery Impact​

Higher sampling rates produce more data but consume more battery. The default configured rates are 5 Hz for the accelerometer and 1 Hz for GPS. In practice, mobile operating systems throttle background GPS delivery — the effective rate is often significantly lower than 1 Hz, particularly when the app is not in the foreground. Rates can be adjusted via the API.

References​