[Therion] SDs for distoX surveys

[Andrew Atkinson]

I try to get people to rotate the distox when taking some/all readings
depending on there keenness and how easy it is*. The distox records and
sends its rotation to pockettopo and I put this into the therion/survex
file. So should the rotated leg have a different sd to the none rotated,
probably. It would be useful if therion/survex could do this automatically
from the readings but I guess that would require there to be a rotation
field in *data

*rotation is a partial check on calibration and generally picks up local
magnetic interference, so at a minimum rotate every 5 or whenever we
suspect metal.

Andrew

On Wed, 15 Aug 2018, 15:23 Footleg, <drfootleg at gmail.com> wrote:

> In my own experience, the most common blunder which the 'measure 3 times'
> method with DistoX2 catches is mis-read distance. The Disto tends to be
> used in the same orientation for all 3 shots, so the compass and clino tend
> to be well aligned in all 3 (regardless of how well calibrated the DistoX
> is, or is there are local magnetic fields throwing the compass). But the
> laser does sometimes miss the target and overshoot, resulting in one of the
> 3 shots being out of tolerance for PocketTopo to count them as a valid leg.
> Of course catching blunders so they never make it into the data (we would
> reshoot when it happens) is not the same as the SD in the measured data.
>
> The way we catch bad calibration problems or local magnetic interference is
> to take backshots (3 of them). This has saved serious errors on multiple
> occasions which would not have been detected taking shots in one direction
> alone.
>
> Footleg
> --
> Survex https://lists.survex.com/mailman/listinfo/survex
>