Exploring the graphical modeler in QGIS 3.0

This video provides an introduction to the QGIS graphical modeler. It was created using a pre-release version of QGIS 3.0 (scheduled to be released Dec 8, 2017). My understanding is that many of the actual algorithms have been reworked under the surface to increase performance, but there are only very minor changes to the graphical modeler user interface. If you are using QGIS 2.xx you should have no problems following this video, although I believe that any models created in 2.xx will need to be redone in 3.xx.

What is the graphical modeler?

If you are used to working in the ESRI ecosystem and are not familiar with the graphical modeler, it plays the same role as the Model Builder in ESRI products. I’m not certain that it is quite as powerful as Model Builder because there are no iterators or branching tools. Nevertheless it allows you to chain together several processing algorithms (geo-processing tools) to perform fairly complex geoprocessing tasks. I found it quite easy to learn and use.

The QGIS geo-processing framework

QGIS has a stunning array of geoprocessing algorithms available for free. It includes well documented and thoroughly tested algorithms from GDAL, GRASS, SAGA, LAS Tools (Lidar processing) and others. It also has the ability to work with algorithms written in R. Like QGIS, all of these algorithms are open source and so, if need be, you can see the actual source code so you can verify exactly what is being done.

This openness can be very important in scientific research applications. Many algorithms published in the scientific literature are implemented first in one or more of these open source toolboxes. Many other tools such as difference and smoothing algorithms for vector layers and most raster processing algorithms are only available with extensions or advanced licensing levels in the ESRI ecosystem.

This video is a combination of two out of about 70 lectures in a course I am creating called QGIS 3.0 for GIS Professionals that should be available within a few days of the release of QGIS 3.0. For more information on this and other courses please see my courses page.

One Reply to “Exploring the graphical modeler in QGIS 3.0”

  1. I just finished watching your video on graphical modeler it was extremely helpful thank you very much for taking the time to produce it! What I want to do is very simple I think but I am not sure what I am missing. I have done similar things in Model builder in Arcmap. I want to create a model in graphical modeler that used the package layers algorithm to create a geopackage nightly which includes all the layers that I edit daily and overwrite the existing one. Once this is done I can export it to a python scrip and schedule it to run nightly. I have the model created but it requires manual input to overwrite the existing geopackage that keeps me from scheduling it to run nightly. Can you help me. Also are you still offering the graphical modeler class on udemy for $20?
    Thanks,
    Henderson County TN E911
    GIS Administrator
    731.358.7932

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