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Tag: guide

ChatGPT for QGIS: What It Can and Can't Do, Tested

Can ChatGPT automate QGIS? I asked it for PyQGIS code on three real tasks and ran every script in QGIS. What worked, what failed without an error, and why.
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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 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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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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Multispectral vs Hyperspectral: Bands, Cost and Free Data

Multispectral records 4 to 13 wide bands, hyperspectral 100 to 300 narrow ones. A table of bands, free satellites, drone sensor cost and data size.
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Plot Plan vs Site Plan: The 8 Items 19 Permit Offices Check

A plot plan draws one lot, a site plan the whole project. The 8 items 19 US permit checklists ask for, who can draw a plot plan, and how to make one in QGIS.
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Orthophoto vs Orthomosaic: The Difference, and 7 Free for QGIS

An orthophoto is one corrected photo; an orthomosaic stitches many. How each is made, why one drew Berlin's TV tower 127 m off, and 7 free national services.
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Semantic vs Instance vs Panoptic Segmentation: The Difference

Semantic segmentation labels every pixel with a class: building or not. Instance segmentation draws every building as its own object.
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Greenfield vs Brownfield Sites: Meaning, Costs, How to Spot Them

A greenfield site was never built on; a brownfield site was, and may hold slabs or pollution. What each costs, how it looks from the air, 314 sites counted.
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