[Therion] Survey altitude in debuggable format

[Tarquin Wilton-Jones]

Is there some kind of debug output that I can get from Therion which
will tell me the altitudes that it picked for its automatic colour bands
(for "color map-fg altitude")?

Obviously, I can see these visually on a PDF, but those numbers are
rounded (I don't know if Therion actually picks "4" or "4.253" as the
actual boundary), and I was hoping they might be in a format that is
more easily machine readable. Perhaps something in thTMPDIR?

Thanks for any info.