Spatial databases can contain millions of geographic objects. In some cases, a PostGIS query may take several seconds — or even several minutes — to execute. This problem often occurs when: In this article, we will…

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…

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…

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…

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…

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…

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…

In QGIS, it is common to associate data from an external table with a geographic layer. For example, you may have a layer of municipalities and a CSV file containing demographic statistics. To combine this information,…

Underwater, different wavelengths of light are progressively absorbed: red disappears first, followed by orange and yellow. Even at shallow depths, photos often have a blue-cyan color cast. As a result, images look bluish or greenish and…

To import a CSV in QGIS, use “Add Delimited Text Layer”, select the file, and define X/Y coordinates. Importing a CSV file into QGIS is a very common task when working with geographic data. Coordinates can…