QGIS
Accessing Basemaps in QGIS Adding Basemap Layers QGIS provides easy access to various online basemaps through the Browser panel. Basemap layers including OpenStreetMap, Bing Maps, Stamen Maps and others can be added with just a few clicks. When a basemap layer is selected, QGIS automatically handles the web map service (WMS) or web map tile…
The QGIS processing framework provides access to hundreds of geospatial analysis tools and algorithms. These tools can be accessed through the graphical user interface (GUI) of the QGIS desktop application. However, the processing framework also offers a scripting and command line interface for advanced users and developers. This article explores techniques for utilizing the processing…
Why Run Algorithms from Scripts? Executing QGIS geoprocessing and spatial analysis tools from Python scripts instead of the graphical user interface offers several advantages: Automation and reproducibility – Scripting workflows allows them to be easily repeated and shared Custom workflows and analysis – Flexibly chain together sequences of tools that would be difficult to do…
Reading Algorithm Output Layers When an algorithm is executed in QGIS, it often generates one or more output layers that are automatically loaded into the QGIS project. However, when running algorithms in standalone PyQGIS scripts, the output layers are not automatically loaded. To access the output layers in PyQGIS, the processing.run() method returns a dictionary…
QGIS offers a robust set of geoprocessing algorithms and spatial analysis tools through its Processing framework. These powerful algorithms can be accessed directly within standalone Python scripts, allowing automation of complex geospatial workflows without the need to create full QGIS plugins. This guide provides practical techniques for calling Processing algorithms from PyQGIS scripts. It covers…
The Problem of Slow Exports Exporting large geographic datasets from spatial databases can be time and resource intensive. Factors like dataset size, complexity, network speeds, and hardware constraints lead to sluggish export speeds. Users experience frustration when pulling data or sharing it with colleagues. Slow exports delay analysis workflows and impact productivity. Technical users need…
Understanding Shapefiles in QGIS A shapefile stores non-topological vector data for use in geographic information system (GIS) software. The shapefile format spatially describes vector features such as points, lines, and polygons representing buildings, roads, and boundaries. When loaded into QGIS Desktop, shapefiles allow users to visualize geographic data, view attribute information, edit geometries and data,…
Quantum Geographic Information System (QGIS) is a popular open-source geographic information system (GIS) application used to view, edit, and analyze geospatial data. When creating maps in QGIS that span the Pacific Ocean, it can be useful to center the map on the Pacific for optimal visualization and analysis. Centering maps over large water bodies like…
Defining the Problem: Imprecise Country Boundaries in Pacific Maps Precisely rendering country borders in geographic information system (GIS) software can be challenging, especially for Pacific island nations. Small errors in coordinate reference systems, extents, projections, symbology, and data resolution can cause misalignments between borders and coastlines, gaps between countries, or other spatial inaccuracies. For example,…
Troubleshooting TypeErrors in Attribute Summations When working with Geographic Information Systems (GIS) data in Python, a common task is summarizing attributes across spatial features. This often involves totalling or averaging numeric fields attached to GIS vectors or rasters. However, these calculations can easily fail with cryptic TypeErrors if attributes have inconsistent data types or invalid…