PostScript (.ps)

PostScript is a page description language invented by Adobe in the early 1980s; PDF grew directly out of it. A .ps file is, in essence, a small program executed by the interpreter inside a printer or a RIP server: it draws vector outlines, text and raster inserts. Level 3 is still understood by office and print-shop devices, and the free Ghostscript opens such a file on any operating system.

An OpenStreetMap map is exported to PostScript when the result goes into a printing or archival pipeline: hand it to a print shop, put it on a RIP, keep the layout in editable vector form for years ahead. For on-screen viewing the format is awkward — usually a .ps is first turned into a PDF with a single command.

Here is how the file is built on our side: QGIS draws the sheet in vector, the labels stay as text with embedded fonts, and then Ghostscript converts the result into PostScript Level 3 with a standard DSC structure. The sheet is 297x210 mm by default (A4 in landscape orientation), raster elements are 300 DPI. PostScript has no layers by the design of the format itself: the map arrives as a single stream of vector commands.