CSV (Comma-Separated Values)

CSV is a simple table: a row per object, columns separated by commas. Geography is put into it in two ways, and we use both at once: the full geometry of an object is written as text in WKT format, and next to it come the latitude and longitude of a representative point — for a line and a polygon that is a point on the object itself, not a nominal center outside it.

The format is chosen when the map is needed as data rather than as a picture: to count objects in a table, to merge with an export from your own system, to load into a database, to hand to a colleague without a GIS, to run through a script. CSV is read by literally everything — from Excel to pandas.

The output is a single file in UTF-8 encoding. One layer gives an ordinary table; if several layers are selected, they are gathered into one file, and the first column _layer shows where the row came from — it makes splitting the data back apart easy. OSM attributes go as separate columns, and the coordinates are in WGS84 rounded to seven decimal places, which is about a centimeter.