Tag: guide

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.

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.

A plot plan draws one lot, a site plan the whole project. We read 19 US permit checklists: the name on the form says little about what the drawing holds.

An orthomosaic is one map-accurate image stitched from many drone or aerial photos. How it is made, how it differs from an orthophoto, and how to use it.

Semantic segmentation labels every pixel with a class: building or not. Instance segmentation draws every building as its own object.

A greenfield site has never been built on. A brownfield site has, and may still hold slabs, sheds or contamination. What each costs and how to tell them apart.

A digital surface model (DSM) is the top of everything: roofs, trees, ground. A digital terrain or elevation model (DTM, DEM) is bare ground. Which to use.

A building footprint is the ground area inside a building's outer walls. What counts, how to calculate it, and where to download free footprints of any city.

GeoAI is machine learning run on geographic data. The five things it extracts today, what it costs in hardware and time, and how to run it in QGIS.