On 2019-08-15 11:50 +0200, Benedikt Hallinger wrote: > To expand a little in this, you could also use the standard „grade“ to tell > theriob which centerline data has which quality. We use this to mark the > centerlines we have surveyed with distox and traditional way and therion uses > this to put more of the errors towards the more bad survey.
What SD numbers do you use for this? I agree they should be different, but I've not seen much research evidence on what the correct numbers are. Also SDs are about expected errors and do not cover blunder probability very usefully, which is also quite different for fully digital and paper-based surveying as well as for compass/clino/tape vs SAP or DistoX. You could adjust the SDs to allow for this, given that we don't have a better mechanism, but again - how do we choose the numbers? I have asked this before and not had useful answers. I have a re-survey project which has found a lot of errors in old (both compass/clino and distoX surveys). I'm struggling to work out what to do with the differences, but it's possible that some plausible blunder probabilities could be generated if enough resurvey is done. The main problem is that the resurvey is wrong too, just by a different unknown amount, and could itself contain blunders. In practice I found it really difficult to refind all the previous stations so the resurveys are not mostly leg-for-leg, just connected every so often. None of that helps much with the fact that survex does its sums as if there are only measurments errors, not blunders. Wookey -- Principal hats: Linaro, Debian, Wookware, ARM http://wookware.org/
signature.asc
Description: PGP signature
_______________________________________________ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
