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…
Mismatching CRS Causing Display Issues Geographic information systems (GIS) rely on coordinate reference systems (CRS) to accurately display locations and geometries of geospatial data layers. When loading multiple GIS data layers into a QGIS project, the layers may have differing original CRS assigned to them. This CRS mismatch can cause various display issues: Layers not…
Understanding Coordinate Reference Systems A Coordinate Reference System (CRS) defines the coordinate system and map projection used to represent geographic data in QGIS. It is critical to properly manage CRS in QGIS projects to ensure accurate analysis and prevent errors due to mismatched CRS between layers. Common issues caused by mismatched CRS include inaccurate distance…
What is a Coordinate Reference System (CRS)? A coordinate reference system (CRS) is a coordinate-based reference framework that is used to represent and identify geographical locations on the Earth’s surface. At its core, a CRS consists of a datum, a coordinate system, and a map projection. The datum provides a reference point relative to the…
What are Coordinate Reference Systems and Why They Matter A coordinate reference system (CRS) is a fundamental component of geographic information systems (GIS) that defines the coordinate system and map projection used to represent the locations and shapes of spatial features on the Earth’s surface. At its core, a CRS provides a reference framework for…
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…
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…
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…
Understanding GIS Basemaps and Their Legal Restrictions Geographic Information System (GIS) basemaps are foundational maps consisting of reference features such as roads, landmarks, and political boundaries used to provide context for overlaying spatial data layers. Basemaps utilize data sourced from satellite imagery, GPS devices, digitized maps, government agencies, and field observations. Sources of basemap data…
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…
