https://spatialthoughts.com/category/qgis/Recent content in QGIS on Spatial ThoughtsHugoen-usFri, 29 Nov 2024 00:00:00 +0000https://spatialthoughts.com/2024/11/29/qgis-coditional-input-model/Fri, 29 Nov 2024 00:00:00 +0000https://spatialthoughts.com/2024/11/29/qgis-coditional-input-model/QGIS Model Designer offers powerful functionality for automating workflows. Many workflows are based on conditional logic that can generate different outputs based on the inputs provided. This post...https://spatialthoughts.com/2024/05/13/30daysofqgis/Mon, 13 May 2024 00:00:00 +0000https://spatialthoughts.com/2024/05/13/30daysofqgis/Welcome to #30DaysOfQGIS! We have launched our Advanced QGIS course on YouTube and have designed this challenge to help you master QGIS! Spend 30 minutes each day for the next 30 days to level-up...https://spatialthoughts.com/2024/04/08/rendering-print-layouts/Mon, 08 Apr 2024 00:00:00 +0000https://spatialthoughts.com/2024/04/08/rendering-print-layouts/When automating GIS workflows, one often needs to automate the creation of cartographic outputs. The QGIS Model Designer allows you to build a workflow by combining multiple Processing algorithms....https://spatialthoughts.com/2023/07/13/pixel-weights-zonal-stats/Thu, 13 Jul 2023 00:00:00 +0000https://spatialthoughts.com/2023/07/13/pixel-weights-zonal-stats/An important concept in spatial statistics is pixel weights. When calculating pixel statistics with a polygon, partial pixel overlaps are treated differently by different packages and you need to...https://spatialthoughts.com/2022/07/30/qgis_process_command_line/Sat, 30 Jul 2022 00:00:00 +0000https://spatialthoughts.com/2022/07/30/qgis_process_command_line/Modern versions of QGIS comes with a handy command-line utility called qgis_process. This allows you to access and run any Processing Tool, Script or Model from the Processing Toolbox on a terminal....https://spatialthoughts.com/2021/06/12/split-polygons-qgis/Sat, 12 Jun 2021 00:00:00 +0000https://spatialthoughts.com/2021/06/12/split-polygons-qgis/In this post, I describe how we can use built-in QGIS processing tools to create a workflow to split polygons into equal parts. Using a clever algorithm and Feature Iterator tool in the Processing...https://spatialthoughts.com/2021/05/14/weighted-centroids-qgis-gee/Fri, 14 May 2021 00:00:00 +0000https://spatialthoughts.com/2021/05/14/weighted-centroids-qgis-gee/In this post, I will outline techniques for computing weighted-centroids in both QGIS and Google Earth Engine. For a polygon feature, the centroid is the geometric center. It can also be thought of...https://spatialthoughts.com/2021/03/15/gis-in-urban-and-regional-planning/Mon, 15 Mar 2021 00:00:00 +0000https://spatialthoughts.com/2021/03/15/gis-in-urban-and-regional-planning/I recently taught a 1-month long course on GIS Applications in Urban and Regional Planning. We explored how GIS can be applied to solve problems in 6 different thematic areas. In this post, I will...https://spatialthoughts.com/2020/11/26/spatial-homogeneity-testing-qgis/Thu, 26 Nov 2020 00:00:00 +0000https://spatialthoughts.com/2020/11/26/spatial-homogeneity-testing-qgis/Rainfall is arguably the most frequently measured hydro-meteorological variable. It is a required input for many hydrological applications like runoff computations, flood forecasting as well as...https://spatialthoughts.com/2020/06/17/fix-nodata-values/Wed, 17 Jun 2020 00:00:00 +0000https://spatialthoughts.com/2020/06/17/fix-nodata-values/When working with raster data, you may sometimes need to deal with data gaps. These could be the result of sensor malfunction, processing errors or data corruption. Below is an example of data gap...https://spatialthoughts.com/2020/04/08/calculating-shared-border-lengths/Wed, 08 Apr 2020 00:00:00 +0000https://spatialthoughts.com/2020/04/08/calculating-shared-border-lengths/In a previous post, I showed how to use the aggregate function to find neighbor polygons using QGIS. Using aggregate functions on the same layer allows us to easily do geoprocessing operations...https://spatialthoughts.com/2019/11/07/random-points-with-distribution/Thu, 07 Nov 2019 00:00:00 +0000https://spatialthoughts.com/2019/11/07/random-points-with-distribution/Generating pseudo-random data is important for many aspects of research work. QGIS provides for many methods of generating random points to facilitate this.https://spatialthoughts.com/2019/09/26/fuzzy-table-joins-in-qgis/Thu, 26 Sep 2019 00:00:00 +0000https://spatialthoughts.com/2019/09/26/fuzzy-table-joins-in-qgis/Table Joins are a way to join 2 separate layers based on a common attribute value. QGIS has a Join Attributes By Field Value algorithm that allows you to perform table joins. A limitation of this...https://spatialthoughts.com/2019/05/23/neighbor-polygons-aggregate-qgis/Thu, 23 May 2019 00:00:00 +0000https://spatialthoughts.com/2019/05/23/neighbor-polygons-aggregate-qgis/Read my previous posts Summary Aggregate and Spatial Filters and Advanced Aggregate Expressions to Automate QA to learn more about the powerful aggregate function.https://spatialthoughts.com/2019/04/19/advanced-aggregate-expressions/Fri, 19 Apr 2019 00:00:00 +0000https://spatialthoughts.com/2019/04/19/advanced-aggregate-expressions/This post is the continuation of Summary Aggregate and Spatial Filters in QGIS. I have been exploring aggregate functions more and have found interesting ways to automate tasks in QGIS. One such...https://spatialthoughts.com/2019/04/12/summary-aggregation-qgis/Fri, 12 Apr 2019 00:00:00 +0000https://spatialthoughts.com/2019/04/12/summary-aggregation-qgis/QGIS expression engine has a powerful a summary aggregate function that can do spatial joins on the fly. This enables some very interesting uses.https://spatialthoughts.com/2019/03/21/animated-flight-lines/Thu, 21 Mar 2019 00:00:00 +0000https://spatialthoughts.com/2019/03/21/animated-flight-lines/You may have seen a map where source and destination points are connected via curved lines. It is possible to create such a map in QGIS with a simple trick - using custom projections and...