Offline Data Collection & Synchronization

Working offline in remote field settings, automatic background sync, conflict resolution, and device storage management.

MQUAD is built from the ground up as an offline-first system. You never need an active internet connection to browse assigned surveys, fill out complex questionnaires, capture photos, record audio, or review collected responses.

1. How Offline Mode Works

  • All assigned survey schemas, version definitions, choice lists, external lookup datasets (CSV/XML), and pre-downloaded map tiles are stored in a high-security encrypted local SQLite database (SQLCipher) on the device.
  • While offline, completed responses are given a cryptographically secure local Response ID (RID), signed with an integrity hash, and stored in the local outbox.
  • When an internet connection becomes available, MQUAD automatically coordinates with the central Sync Service to transmit pending records without interrupting your fieldwork.

2. Sync Execution Modes

MQUAD supports three coordinated synchronization triggers:

1. Foreground Sync (Immediate)

When the app is open and internet connectivity is detected:

  • The sync engine listens for local state changes.
  • Within 2 seconds of completing a form or making edits, transmission begins automatically.

2. Background Periodic Sync

When the app is minimized or the screen is turned off:

  • On Android & iOS, background worker tasks trigger approximately every 15 minutes.
  • Background sync activates only if:
    • Network connectivity is active.
    • Device battery level is greater than 20% (to prevent draining enumerator devices in the field).
  • On Desktop, sync runs in a lightweight background isolate every 15 minutes.

3. Manual Sync

  • Tap the Sync Now button on the Home dashboard at any time.
  • Or perform a pull-to-refresh gesture on the Surveys, Responses, or Drafts lists.

3. Visual Sync Status Indicators

Every survey, draft, and completed response displays a distinct sync indicator badge:

IndicatorStatus NameDescription
🟢 Green CheckmarkSyncedResponse is confirmed received, verified, and saved on the central server.
🔄 Spinning ArrowsSyncingData or media chunks are currently transmitting to the server.
🟡 Yellow ClockPending UploadResponse is completed on the device and waiting in the queue for a network connection.
⚫ Grey Cloud SlashOffline QueueDevice is currently offline; records will transmit automatically once reconnected.
🔴 Red ExclamationSync Error / ConflictSubmission requires review or conflict resolution before finalization.

4. Bandwidth & Network Data Controls

To conserve mobile data allowances when operating over cellular connections:

  1. Open Settings → Sync Settings.
  2. Sync Over Wi-Fi Only: When enabled, MQUAD pauses automatic upload of heavy submissions and media until the device connects to an authorized Wi-Fi network. Urgent text-only responses can still be manually synced if needed.
  3. Block Sync While Roaming: Automatically blocks data transfer when your device is connected to international or out-of-region cellular roaming networks.

5. Media Synchronization

Surveys with photos, signatures, audio recordings, or videos can generate significant data volume:

  • Automatic Pre-Compression: Images and videos are compressed on-device immediately upon capture using optimized quality curves.
  • Chunked Resumable Uploads: Large media files are uploaded in chunks. If the cellular connection drops halfway through a photo upload, transmission resumes from the last confirmed chunk when the network returns.
  • Media Gate Check: Before beginning interviews, MQUAD checks that all required survey media assets (e.g. choice images, audio prompts) are downloaded and verified.

6. Conflict Resolution

In rare instances where a record has been edited on the web dashboard while simultaneous offline edits occurred on a mobile device:

  1. A Conflict Alert banner will appear on the Home dashboard and under Settings → Conflicts.
  2. Tap on the conflicted response to open the Conflict Resolution Screen.
  3. MQUAD displays a side-by-side comparison of:
    • Local Version: The answers and timestamp recorded on your mobile device.
    • Server Version: The answers and timestamp stored on the central server.
  4. Resolution choices:
    • Keep Local: Overwrites the server record with your mobile device's answers.
    • Keep Server: Discards the local changes and accepts the central server's record.
    • Resolve All: If multiple conflicts exist, batch-applies your preferred rule across all items.

7. Device Storage Management

Field campaigns that run for weeks or months can accumulate thousands of responses and gigabytes of photos:

  1. Open Settings → Storage.
  2. The visual storage gauge shows internal device capacity:
    • Green: Normal (< 80% used).
    • Amber Warning: Storage reaches 80%—cleanup recommended.
    • Red Critical: Storage reaches 95%—submission capture may pause until space is freed.
  3. Safe Cleanup Actions:
    • Clear Synced Media Cache: Deletes local cached copies of photos that have already been confirmed synced to the server. (Unsynced media is never deleted).
    • Clear Offline Map Tiles: Frees storage used by cached map tiles without deleting survey data.
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