[Therion] Cartesian STD for individual legs

[Tarquin Wilton-Jones]

Hi Marcelo,

> These surveys  only
> use tape and clinometer, surveying triangles, starting from two
> coordinates known  stations.

That's ... both cool and insane at the same time.

Pretty sure a Total Station can cope with this magnetic rock situation.
Perhaps someone else on this list can offer advice...

> Is there a way to specify specific standard deviations for each leg in
> Therion?

As far as I know, SD affects all legs specified after it, until another
sd command changes it. Similar to the "calibrate" command or "units"
command.
sd compass 0.3 degrees
1 2 12.5 315 17
sd compass 0.5 degrees
2 3 7.2 220 33

It is a Survex command (most things inside a Therion centreline block
are a direct copy of their Survex equivalents, and can be passed through
to Survex for processing; group/endgroup is an exception, which is
begin/end in Survex syntax).

I tested it with a loop where every leg is set to sd 0.1, but one single
leg set to 200. Therion gave that single leg most of the error.

If that doesn't work for you, you can use:
group
sd compass 0.3 degrees
1 2 12.5 315 17
endgroup
group
sd compass 0.5 degrees
2 3 7.2 220 33
endgroup

It's quite verbose, but that is explicitly stated as being possible in
the Therion book.

Hope this helps.

Tarquin