Posts by TerraLab

How to digitize a map in QGIS: draw polygons by hand with snapping and tracing, trace a scanned map, convert a raster, or let AI outline every object at once.

How to do a spatial join in QGIS: join attributes by location or by nearest, count points in polygons, pick the right predicate, and avoid the CRS traps.

AI now digitizes, scripts and runs whole QGIS tasks. US mapping jobs are still projected to grow to 2035. Here is what changes, task by task, and what to learn.

Over one Pyrenean valley, four free 30 m DEMs sat 12 to 18 m above the LiDAR ground under forest. Where to get each DEM free, and how to load it in QGIS.

One story is 3.07 m (10.1 ft) floor to floor at the median. Heights for 1 to 12 stories: a 5-story building stands 16.2 m (53 ft), a 10-story one 27 m (89 ft).

6,041 bike crashes in Paris mapped three ways in QGIS: Heatmap renderer, kernel density raster and hexagons, then one sentence to an AI agent: 2 min 34 s.

Microsoft matched 25% of a French town's cadastre buildings, OpenStreetMap 83%. Then Nairobi: five free sources, timed downloads, checked on drone imagery.

KML is map data written as XML; a KMZ is the zipped form. Open it in Google Earth or QGIS, find attributes hidden in HTML, convert to Shapefile, CSV or GeoJSON.

NDVI flattens out over dense canopy. EVI, SAVI, NDRE, NDWI and NDMI each fix a blind spot. Raster Calculator formulas and a measured test in Brazil.

8 sources from Landsat to Pléiades Neo, with price and revisit. On one suburb, 0.2% of buildings cover 16 pixels at 10 m and 96% at 50 cm, of 20,911 counted.