Filtering Map Features Based on Atlas Coverage Layer Geometry or Attribute in QGIS 3.0

When working with Geographic Information Systems (GIS) and the powerful data analysis tool QGIS 3.0, it's often necessary to focus on specific areas or conditions within your data. One of the key features that helps achieve this is the Atlas mechanism, which allows you to control the visibility of map features based on different criteria. This article will guide you through two primary methods: filtering by using the Atlas coverage layer geometry and by utilizing attributes.

Filtering via Atlas Coverage Layer Geometry

To filter the visibility of map features based on the Atlas coverage layer geometry, QGIS 3.0 offers a straightforward yet effective approach. Here’s how you can do it:

Select the Coverage Layer: Ensure that your coverage layer is selected in the Layers panel. The coverage layer acts as the initial reference point for filtering.

Access Atlas Generation Options: Switch to the Print Layout view and open the Atlas generation options dialog box from the Layout menu. This dialog provides you with the necessary controls for customization.

Choose the Filtering Method: In the Coverage layer drop-down menu, select the layer you wish to use for filtering. You have two methods to choose from:

Single Feature: Features that intersect with the currently selected feature in the coverage layer will be visible. Polygon Layer: All features within the currently selected polygon will be visible, regardless of their intersection with the coverage layer.

Filtering via Attribute

In addition to filtering by geometry, you can also control the visibility of map features based on specific attributes. Here’s how to achieve this:

Select the Filtering Method: Again, switch to the Print Layout view and open the Atlas generation options dialog box from the Layout menu. This time, focus on the Filter drop-down menu.

Select the Attribute: Choose the attribute that you want to use for filtering. You have two options:

Single Value: Features that have the selected attribute value will be visible. Range: All features that have an attribute value within the specified range will be visible.

Example Scenarios

Scenario 1: Filtering by Polygon Layer

Imagine you have a map detailing different land uses in a city. You want to focus on areas where commercial development is planned. Your coverage layer is a polygon layer of urban development zones. By selecting this polygon layer and setting the filtering method to “Polygon Layer,” you ensure that all map features (like buildings, roads, etc.) within those zones are visible. This approach is ideal for high-level overviews or specific thematic themes within a larger map dataset.

Scenario 2: Filtering by Attribute

Suppose you are working with environmental data and want to highlight specific types of pollution levels across different regions. In this case, you might filter by attributes like “Pollution Index” to show all areas within a predefined range (e.g., pollution levels from 40 to 70). This method is particularly useful for data analysis and highlighting patterns or trends.

Conclusion

QGIS 3.0 offers a robust and flexible Atlas feature for detailed and thematic mapping. Whether you need to focus on specific geometries or attributes, you can effectively control the visibility of map features to meet your specific needs. This functionality is invaluable for data analysts, cartographers, and GIS professionals who require precise control over their visualizations.

Related Keywords

QGIS 3.0 Atlas Coverage Layer Attribute Filtering GIS QGIS Atlas