Sync Data from Multiple QField Users to QGIS

Introduction

In work and fieldwork, several people often split the tasks. Have you ever been unsure how to efficiently sync and merge data that multiple users collected in QField into QGIS?

This article explains how to sync field survey data to QGIS.

The basic flow is to transfer each user's updated QField project to the PC that stores the QGIS project, and then use the QFieldSync plugin to sync that data automatically.

Overview of syncing with the QFieldSync plugin

You can sync data by transferring the QField project to a PC and opening it in QGIS, but when several people update data from different QField devices, the data can conflict or go missing. The sync feature of the QFieldSync plugin avoids this. It consolidates everything that multiple users added into the original QGIS project without loss.

In the figure below, for example, devices A and B both edit the same QField project, and each adds features to the same layer. With the QFieldSync plugin, you can merge both sets of changes into the original layer.

How to sync a QField project to a QGIS project

To sync QField projects from multiple users, first set up the QGIS project for offline editing and distribute it to the QField users. Then sync the data each user collected back into the original QGIS project.

The steps below cover the setup and the sync.

Set the QGIS project layers for offline editing

Use the QFieldSync plugin to transfer a QGIS project to a mobile device.

To enable syncing by multiple users, set the target layers in the QGIS project for offline editing before you transfer the project to the mobile device.

To do this, choose Project → Properties from the menu bar.

In the Project Properties dialog, select the QField tab.

Click the Cable Packaging tab to set the Packaging Action for each layer you want to sync. This setting defines the action performed on each layer when you create a QField package. With the default Copy action, the plugin simply copies the file for the layer into the package.

However, simply copying the data cannot manage conflicts with other updates when you sync. So set the Offline editing option for the layers you edit in QField.

With this option, the plugin copies the layer to the package folder as a working copy and logs every change made during the field survey. When you sync to the original project, the plugin uses this log to prevent conflicts between changes by multiple users and apply the changes to the original source layer correctly.

To exclude a layer you do not use in QField from the QField package, set its action to Remove from project.

When the settings are done, use the QFieldSync plugin to create a QField package and transfer it to the mobile device, and collect data in the field.

Sync data from QField

When the fieldwork is done, transfer the QField data back to the PC. After you transfer the QField project to the PC, extract the zip file.

Next, sync the changes in the QField project to the original QGIS project.

First, open the original project in QGIS. The features you added in QField are not in the project yet, because the QField changes are not synced.

Next, click the Synchronize from QField button on the QFieldSync toolbar.

The Synchronize Project dialog opens. Set it up as follows.

1. Next to Select the QField Project Folder, click the ... button and select the QField project folder you transferred from the mobile device.
2. In the Directories to be copied section, click the Refresh directories button to list the folders in the project you selected. Check the directories that contain images and other files to sync those files too.
3. When the settings are done, click the Synchronize button to start the process.

When the process finishes, the changes in the QField project merge into the QGIS project, and the features you added in QField appear correctly.

Apply changes from multiple users

Sync the data that other users collected in the same QField project to the original QGIS project with the same steps. The data the first user registered stays, and the newly added features appear in the original QGIS project.

Cautions when syncing with QFieldSync

Syncing with QFieldSync is convenient when multiple users edit data in the same QField project, but conflicts can occur when you edit existing features. For example, editing the attributes of the same feature, adding photos to it, or correcting its position can cause conflicts.

In this case, the changes from the QField project synced later take priority, so the changes from the project synced earlier may be lost. To prevent such conflicts, assign each user a different area to cover and avoid having multiple people edit the same data at the same time.

On the other hand, adding only new data does not usually cause conflicts. You can therefore use this sync method with confidence even when several users enter data in the same area at the same time.

Conclusion

This article showed how to export data collected in QField and sync it efficiently to a QGIS project. The sync feature of the QFieldSync plugin can manage updates from multiple users. However, especially when you modify existing data, take care that the editing areas do not overlap.

This method requires you to transfer the QField package manually every time, but QFieldCloud lets you update data more efficiently and smoothly. For details, see the following article.