[Therion] Two extended profiles for same survey

[Tarquin Wilton-Jones]

> Is it possible to work around this problem?

Yes but no.

This is why Bruce (?) recommends keeping your "extend" directives in a
totally separate document. You can have
survey/subsurvey/subsurvey.th
survey/subsurvey/extendv1.th
survey/subsurvey/extendv2.th
and in subsurvey.th you use:

input extendv1.th

when you want to use that version. Manual editing of the files is
required. Annoying, I know.

You can make life easier with a top level file (whole map, not
subsurvey) specifying the full set of "extend" commands for all
subsurveys at once. Then you only need a single edit to swap out the
extended elevation for the entire survey.

Unless maybe there is some mechanism I don't know about.