[Therion] SDs for distoX surveys

Graham Mullan graham.mullan at coly.org.uk
Sun Aug 5 08:44:43 CEST 2018

I am not sufficiently versed in the maths to suggest what figures might be
used, but I do want to know why you think that the 3-times feature might
affect the expected error for the angles but not for the length?


-----Original Message-----
From: Survex <survex-bounces at survex.com> On Behalf Of Wookey
Sent: 04 August 2018 01:37
To: Survex User Group <survex at survex.com>; Therion List <therion at speleo.sk>
Subject: SDs for distoX surveys

Has anyone thought about what the correct SDs for distoX/distoX2 (as opposed
to compass and tape) surveys are?  I reckon distoX surveys have
significantly lower expected error, due to the 'measure 3 times'
leg feature (if used) and just higher accuracy due to instrument itself,
ease of taking readings (no need to get head near station), and no
difficulties with steep legs > 15 degrees.

Seems to me this means that we should be using different SDs for these
surveys (at least for bearing and inclination readings - length is not
obviously more reliable), but I'm not sure how to quantify those

Anyone got any ideas what numbers to use?

Principal hats:  Linaro, Debian, Wookware, ARM http://wookware.org/

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