[Therion] Handling of tape and backtape in survey data

[Tarquin Wilton-Jones]

On 27/12/2021 19:15, Martin Sluka via Therion wrote:
> 
> 
>> 26. 12. 2021 v 19:32, Tarquin Wilton-Jones via Therion
>> <therion at speleo.sk <mailto:therion at speleo.sk>>:
>>
>> However, for Disto
>> surveying, it feels largely unnecessary, as the accuracy is already a
>> lot more than most surveys need when just using forward sightings.
> 
> But because DistoX is an electronic device it is only way to be sure it
> works properly. The same as check, if three (four) readings for
> surveying leg with rotation around the longitudinal axe of DistoX are in
> tolerance interval.

Oh very true. This is one of the checks I recommend performing
occasionally to test calibration (or every leg when working around
scaffolding or magnetic rocks). Create legs with one reading flat, one
rotated 90 degrees longitudinally, another reading flat or in any other
orientation. Then validate with a splay back to the previous station.

But personally I consider the leg forward, then duplicate backsighted
*leg* for every single leg, to be largely overkill. There are already 3
readings for every leg, and a rotational test (with optional backsight
splay) already serves the purpose of testing calibration and magnetic
effects. And standard leapfrogging can already counteract clinometer
calibration faults.

But I am sure someone will have their reason to make each leg from 6
readings. :)