Elevation grid (XYZ / ASC / CSV)

XYZ heights is a terrain grid written as plain text: not a picture and not a binary raster, but lines carrying the elevation in metres above sea level. There are three written forms, chosen by an option on the order: elevation.xyz — three columns, "X Y Z", separated by a space and with no header line; elevation.csv — the same values comma separated and with an X,Y,Z header; elevation.asc — an ESRI ASCII Grid, which always travels with elevation.prj carrying the coordinate system. The data is identical in all three forms, only the writing changes, so a typo in the option never fails the order: you get the default, XYZ. Delivery is a ZIP: the grid file and README.txt.

The heights come from the global Copernicus DEM GLO-30 model: about a 30 m step with a vertical accuracy of roughly 2–4 m. The value is written with one decimal place — a second one would be invented at that accuracy. That is enough for pre-design assessment, tourism, visualisation and 3D — and not enough for engineering design, grading or any work held to building codes, where an instrumental survey is required. Take this format for the numbers themselves, opened by whatever is at hand — Notepad, Excel, pandas, QGIS, GRASS, Civil 3D — and opened with no GIS at all.

Text has its price: one cell is a whole line of characters, and 64 million cells written as "X Y Z" would come to some 1.6 GB that nothing on your machine would open. Hence the ceiling of 4 million cells: a large area is read coarsened, and the coarsening is spoken in a warning on the order rather than happening silently. Where there is no elevation at all — open sea, a gap in coverage — you get an honest refusal in words, not an empty file. The format is free, with no key and no registration; the attribution line sits in README.txt inside the archive.