Mergin Maps

# How to Set Up Snapping for Mergin Maps Mobile App

since QGIS plugin 2022.5

Capturing data in the field using Mergin Maps mobile app can be easier, if you can snap the vertices of new features to existing geometries. Snapping can also help you avoid creating topological errors in your datasets.

Mergin Maps QGIS plugin provides three snapping options:

  • No snapping - snapping is not enabled (default)
  • Basic snapping - features are snapped to the vertices and segments of vector features in the project
  • Follow QGIS snapping - uses the snapping preferences defined in the QGIS project

# Basic snapping

To set up basic snapping:

  1. Open your Mergin Maps project in QGIS

  2. Go to the Project Properties
    QGIS project properties

  3. Navigate to the Mergin Maps tab and change the snapping settings to Basic snapping
    Mergin Maps snapping options

  4. Apply the changes, save and sync your project.

    Don't forget to synchronise the project also in Mergin Maps mobile app before the fieldwork.

Now you can use basic snapping in Mergin Maps mobile app!

When capturing a new feature near an existing one, the crosshairs will turn purple and snap to its vertex (left) or to its segment (right).
Mergin Maps mobile app crosshairs when snapping

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If you don't want the crosshairs to snap to a feature, try zooming in. The snapping threshold is 20 pixels, so the more you zoom in, the closer you can place the vertex to the existing geometry without snapping.

If you want to change the snapping threshold, use the Follow QGIS snapping option and define the snapping tolerance in your Mergin Maps project in QGIS.

# Follow QGIS snapping

The QGIS plugin gives you the option to use the snapping preferences defined in QGIS project. This means you can, for instance, exclude some layers from snapping, choose the snapping mode or change the snapping threshold.

  1. Navigate to the Mergin Maps tab in the Project Properties and change the snapping settings to Follow QGIS snapping
    Mergin Maps follow QGIS snapping

  2. Enable snapping in the Snapping toolbar and set your snapping preferences.
    QGIS enable snapping

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    If you cannot see the Snapping toolbar in QGIS, ensure it's enabled under View (top-level menu) > Toolbars

  3. Snapping preferences can also be set through the Snapping Options in the Project menu
    QGIS snapping options

  4. Switch to Advanced Configuration
    QGIS advanced snapping configuration

  5. Here, snapping settings can be defined for each layer individually:

    • enable/disable snapping for specific layers. Layers that are not checked will not be used for snapping.
    • in the Type column, you can choose if you want to snap to vertices, segments or both
    • set the Tolerance (the snapping threshold). This defines how close the crosshairs need to be to an existing feature to snap to its geometry.

    QGIS snapping settings

  6. Save and sync your project.

    Don't forget to synchronise the project also in the mobile app before the fieldwork.

Snapping in Mergin Maps mobile app will now follow the snapping settings as defined in the QGIS project.

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You can learn more about snapping in QGIS in QGIS Documentation QGIS User Guide (opens new window).

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