There is no "standard" for XYZ data, it's more or less just an ad-hoc solution, and everybody does as they please.
Regarding Archicad: It's quite picky...
First of all, it's okay to have mixed data. If Archicad finds any non-numerical input the whole line will be discarded as a comment.
Also it is okay to have a numerical IDs for each row (making 1+3 columns).
Just be sure that every row has the same number of columns. The seperator also needs to be the same. Allowed seperators are Space, Tab, Semicolon (;). Also Periods (.) and Commas (,) are accepted, but I highly discourage their use because they will get confused for a decimal seperator easily by humans.
And of course there must not be any missing data.
This and wrong seperators I found to be the most common cause of mishaps.
Mostly AC 26 on Mac | Author of SelfGDL | Developer of the GDL plugin for Sublime Text
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