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Author: Atilio Francois

6 May 20263 May 2026 Atilio Francois No Comments
  • Postgis

[EN]ST_Intersects vs ST_Within: Understanding Spatial Relationships in PostGIS

When working with PostGIS, understanding spatial relationships between geometries is essential for building efficient queries. Two of the most widely used functions—ST_Intersects and ST_Within—are often confused, yet they serve different purposes. In this guide, you’ll learn…

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29 April 202623 April 2026 Atilio Francois No Comments
  • QGis
  • Tutorial

[EN]How to Georeference an Image in QGIS (Step-by-Step Guide)

Georeferencing in QGIS is an essential technique that allows you to align an image with real-world geographic coordinates using control points. Whether you’re working with a scanned map, a PDF plan, or an image without spatial…

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22 April 202616 March 2026 Atilio Francois No Comments
  • QGis

[EN]Cloud-Optimized GeoTIFF (COG): A GeoTIFF Designed for the Cloud

Cloud Optimized GeoTIFF (COG) has become a key format for distributing geospatial rasters over the Internet. Unlike standard GeoTIFF, it allows GIS software such as QGIS to read only the necessary portions of a file stored…

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15 April 202616 March 2026 Atilio Francois No Comments
  • QGis
  • Tutorial

[EN]Shapefile vs GeoPackage: Which Format Should You Choose?

When working with geographic data in QGIS, several file formats can be used to store vector layers. Two formats are particularly common: Shapefile and GeoPackage. Shapefile is a historical format that has been widely used since…

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8 April 202615 March 2026 Atilio Francois No Comments
  • QGis
  • Tutorial

[EN]EPSG:4326 vs EPSG:3857: Understanding the Difference Between the Two Most Common GIS Coordinate Systems

When working with geographic data in QGIS or in web mapping applications, two coordinate systems appear very frequently: EPSG:4326 and EPSG:3857. These two systems are used in many contexts, but they do not represent coordinates in…

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1 April 202615 March 2026 Atilio Francois No Comments
  • QGis
  • Tutorial

[EN]Understanding Projections in QGIS: A Simple Guide

Projections and coordinate reference systems (CRS) are essential concepts when working with geographic data in QGIS. Incorrect handling of projections can cause significant misalignment between layers. When working with geographic data in QGIS, projections and coordinate…

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  1. Atilio Francois on How to develop an application with pgrouting in Windows (1)25 August 2025

    You're right — since 2019 Geofabrik no longer provides plain `.osm` files, only the compressed `.osm.pbf` format. The tool **osm2pgrouting**…

  2. Simon on How to develop an application with pgrouting in Windows (1)25 August 2025

    The osm downloads don't appear to be available, just osm.pfb And osm2pgrouting on Windows doesn't like pbf "not well formed…

  3. Arno on Portable version of QGis 3.32.021 August 2025

    I just want to thank you. It works.

  4. Atilio Francois on Portable version of QGis 3.32.015 May 2025

    What is the link between the qgis update and the portable version? A portable version cannot be updated; it must…

  5. Hugo on Portable version of QGis 3.32.014 May 2025

    For me, the error message complaining that qgis_app.dll is missing started appearing following the most recent QGIS update.

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