QGIS plugin

QGIS plugin#

xDEM offers a graphical user interface (GUI) in the form of a QGIS plugin. This interface provides access to most of xDEM’s features without requiring programming skills.

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QGIS is an open-source geographic information system (GIS). This software allows users to view and process geospatial data in order to extract information from it. Available on all platforms (Linux, Windows, macOS), QGIS provides a wide range of processing and analysis tools. To supplement the basic functionality, extensions can be added, known as plugins. These are small modules that connect to the main software and communicate with it through a Python API.

Important

The QGIS plugin is a recent feature! Its interface and installation process are subject to evolution based on user feedback for future releases.

Installation#

The plugin is available on the official QGIS portal, here are the installation steps:

  1. In QGIS go to Plugins > Manage and Install Plugins... > Not installed.

  2. Search for xDEM.

  3. Click on Install Plugin.

If you need a specific version, you may download it directly from the QGIS website.

  1. Search for xDEM.

  2. Download the ZIP file corresponding to the desired version.

  3. In QGIS, go to Plugins > Manage and Install Plugins... > Install plugin from zip.

It will take a few minutes for the dependencies to install correctly, do not force QGIS to close.

Once installation is complete, xDEM will appear in the Processing Toolbox Image.

Important

The plugin is currently available on Linux and Windows. However, configurations are extremely diverse, whether in terms of the QGIS version or Python version, so compatibility issues may occur.

Getting started#

Most of xDEM’s algorithms are integrated into the plugin, all available in the Processing Toolbox, located on the menu bar at the top of the software interface.

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Once the toolbox is open, xDEM’s algorithms appear at the bottom, in a dedicated section.

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To get started with the plugin’s features, here are two examples, a coregistration followed by deriving the slope. The dataset used is the same as that used in the other xdem examples, which is Longyearbyen, described in Data examples.

Coregistration#

The coregistration methods available in the Python API (Summary of supported methods) are also included in the plugin, each with its own dedicated interface. Inputs can be layers that are already loaded in QGIS or files directly on disk. Outputs can be saved to temporary files (by default) or written on disk. Here is the co-registration interface for the Least Z-difference method.

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Note

For the advanced parameters, the default settings are the same as those in the API. Blockwise mode is also available (Dividing coregistration in blocks), it is normally accessed via the BlockwiseCoreg object and is provided here as the advanced parameter blocksize, by default, it is disabled (value 0).

Once the processing is complete, the log section provides information about the Coregistration metadata.

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These data can then be saved as a text file using the button in the lower right corner of the panel.

Terrain attributes#

The Terrain attributes specific to the xdem.DEM object are also included in the plugin. Here is an example of the slope processing interface configured with the Horn method.

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For all of the plugin’s algorithms, once processing is complete, the output file is opened in the current project. This feature can be disabled thanks to the checkbox Open output file after running algorithm, if visualization in QGIS is not necessary or if the dataset is too large.

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Workflows#

The two workflows presented in xDEM via the Command line interface have also been implemented in the plugin. To use them, you don’t need a configuration file, unlike the Command line interface, everything is directly configurable in the QGIS interface.

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The process generates several output files, exactly the same set you’d obtain with Command line interface: a folder containing raster(s), PNG figures, statistical tables, and both HTML and PDF reports. When the process is complete, the PDF report can be opened in your default browser thanks to the checkbox Open PDF report.

Pipeline building#

QGIS offers a feature for creating pipelines through a graphical interface called the Model Designer. This tool is accessible via the Processing section of the menu bar. Its detailed functionality is described in the QGIS documentation.

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Using the Model Designer, you can create your own workflows. For example it’s possible to create coregistration pipelines with xDEM or even combine them with native QGIS operations. Here is an example of a coregistration pipeline, followed by a calculation of elevation difference.

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This pipeline combines two methods, Iterative closest point, and Nuth and Kääb (2011), then the difference is calculated using the QGIS Raster Calculator. In terms of outputs, two are generated, the aligned DEM and the final elevation difference.