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Tag: qgis

What Is a CRS in GIS? EPSG Codes and Fixing Wrong Layers

A CRS tells software where coordinates sit on Earth. Datums, EPSG codes, 4326 vs 3857, and a step-by-step fix for a layer that lands in the wrong place.
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What Is NDVI? Formula, Value Chart and the Sentinel-2 Trap

NDVI = (NIR - Red) / (NIR + Red), from -1 to 1. What each value range means, a season measured field by field, and the offset that turns 0.82 into 0.56.
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What Is PyQGIS? A First Script and a Chatbot Code Test

Where to run PyQGIS, a first script, and a test on six tasks: chatbot code always ran, but one result was silently wrong when given only layer names.
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What Is QGIS? Free GIS Software, QGIS 4, and the 10 Top Plugins

QGIS is free, open-source GIS for Windows, macOS and Linux. What people use it for, what QGIS 4 changed in 2026, and the 10 most downloaded of 3,600 plugins.
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Download Sentinel-2 Images in QGIS: 4 Free Methods

Stream Sentinel-2 over STAC with no account, or get the L2A product from Copernicus Browser. Four methods tested on farms in Brazil, with timings.
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How to Download OSM Data in QGIS: 4 Methods, Timed

QuickOSM fetched 4,560 buildings in 5 seconds; a whole country timed out. When to use QuickOSM, a Geofabrik .pbf (Kenya in 57 s), Overpass Turbo or an AI agent.
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How to Georeference an Image in QGIS: 3 Ways, on a 1947 Map

Layer > Georeferencer, 8 points, Polynomial 1 and a 34 s warp on a 1947 scan. Which transformation to pick, and why an RMSE of zero hid a map 594 m off.
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How to QGIS 4.2 on Linux Mint (Sept ā€™26)

For a while now, my preferred way of installing QGIS has been from conda-forge. However, while weā€™re waiting for QGIS 4 to become available on conda-forge, there are alternatives:

Option 1: Flatpak

In the Software Manager, you can find QGIS from Flathub in two different versions: stable and lts. And stable should give you 4.2 (even if the Software Manager preview shows an older one):

Option 2: Meet the official QGIS Docker Images

First off, youā€™ll need Docker. If you havenā€™t installed it yet, itā€™s directly available from the Linux Mint Software Manager:

From there on, we just switch to the Terminal for the rest.

If you get ā€œpermission denied while trying to connect to the docker APIā€ when running any of the following commands, you may have to add your user account to the docker group:

sudo usermod -aG docker $USER
newgrp docker # or just log out and back in

Afterwards, it should be straightforward to get the image from Docker Hub, e.g.:

docker pull qgis/qgis:4.2.2-questing

And once itā€™s downloaded, we can launch QGIS:

xhost +local:docker
docker run --rm -it --name qgis \ 
  -v /tmp/.X11-unix:/tmp/.X11-unix \ 
  -e DISPLAY=$DISPLAY \ 
  qgis/qgis:4.2.2-questing qgis

VoilĆ”, QGIS 4!

To persist your QGIS profile/settings across container runs, mount a local folder to the config path, e.g.:

docker run --rm -it --name qgis \ 
  -v /tmp/.X11-unix:/tmp/.X11-unix \ 
  -e DISPLAY=$DISPLAY \ 
  -v ~/.qgis-docker-profile:/root/.local/share/QGIS \ 
  qgis/qgis:4.2.2-questing qgis

Of course, last but not least, weā€™ll also need access to our data, so letā€™s mount a data directory as well, e.g.:

docker run --rm -it --name qgis \
  -v /tmp/.X11-unix:/tmp/.X11-unix \
  -e DISPLAY=$DISPLAY \
  -e LIBGL_ALWAYS_SOFTWARE=1 \
  -v ~/.qgis-docker-profile:/root/.local/share/QGIS \
  -v /mnt/ssd1/Geodata:/data \
  qgis/qgis:4.2.2-questing qgis

Fancy a bit of a stress test? I happened to find a project file written by QGIS 2.19 šŸ«¢

Yes, my friend, this project file is indeed a litte bit older ā€¦ but hey, that doesnā€™t look too bad at all! Some icons seem to be off but, otherwise, looks like winter is coming.

On a side note, whom do I need to ping to the QGIS logo in the System Package / Software Manager updated?

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LiDAR HD from IGN: download and open in QGIS

The classified LiDAR HD cloud covered 78.4% of France on 6 September 2026, 30,933 of 34,877 communes. Map per commune, products, clicks in QGIS.
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Photogrammetry vs LiDAR: Which One for Which Job

Photogrammetry rebuilds a surface from overlapping photos. LiDAR measures it with a laser. One gives colour and a cheap flight, the other sees under the trees.
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