May be just calculate SD for each of 3 repeated measurements, then for all of 'SDs of 3' calculate some stats and use it?
But from theoretical point of view problem of least squares adjustment just can contain all the data, i.e. all repeated measurements while distributing errors, and as secondary result of adjustment will provide the SD. But it is needed to modify loop-closure code, ofcourse, probably using 'ceres-solver lib'... Just for reference of theoretical thinking above, here is a nice book https://www.amazon.com/Observations-least-squares-civil-engineering/dp/0700224815/ref=sr_1_1?ie=UTF8&qid=1534332549&sr=8-1&keywords=e+mikhail+observations+and+least+squares On Sun, Aug 5, 2018 at 12:16 PM, Wookey via Therion <therion@speleo.sk> wrote: > On 2018-08-05 08:44 +0200, Graham Mullan wrote: > > 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? > > The 3-times thing greatly reduces blunders. Blunders are usually in > compass and clino readings, rather than length readings. But you are > right that the 3-times measurement improves all 3 readings (I assume > that's what you were implying). > > Now the SD doesn't represent blunder frequency as it's really about > expected mesurement error, but in practice we use it for blunder > distribution too, so that's why a lower SD for surveys done this way > makes sense to me. If we put in all three versions of the leg then we > could leave the SDs the same, but that's not often done (depending how > you get your data out of a distoX). > > Similar considerations apply to backsighted surveys, where both sets > of readings _are_ normally entered. > > Wookey > -- > Principal hats: Linaro, Debian, Wookware, ARM > http://wookware.org/ > > _______________________________________________ > Therion mailing list > Therion@speleo.sk > https://mailman.speleo.sk/listinfo/therion > >
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