I think there are two issues here. I have skewed surveys built on 2D data using 3D fixed points and that seems, to me, to be what is happening here. Firstly, if your radiolocation point has no depth information then you cannot use it for a 3D skew which I think (I may be wrong) as it is insufficiently accurate. Secondly, if your survey is both only in 2D and has an apparent error of as much as 150 m from the radiolocation point then there is something wildly wrong with the data. Your best bet - and yes I have been forced to do exactly this - is to resurvey the cave to 3D standards, whether this be compass/clino or Distox and start again. Sorry, but your dataset is simply not good enough. Graham -----Original Message----- From: Therion <therion-bounces@speleo.sk> On Behalf Of therion-request@speleo.sk Sent: 22 August 2018 12:00 To: therion@speleo.sk Subject: Therion Digest, Vol 152, Issue 9 Send Therion mailing list submissions to therion@speleo.sk To subscribe or unsubscribe via the World Wide Web, visit https://mailman.speleo.sk/listinfo/therion or, via email, send a message with subject or body 'help' to therion-request@speleo.sk You can reach the person managing the list at therion-owner@speleo.sk When replying, please edit your Subject line so it is more specific than "Re: Contents of Therion digest..." Today's Topics: 1. Re: Fix station point using only 2D (kevin dixon) 2. Re: Fix station point using only 2D (Martin Sluka) 3. Re: Fix station point using only 2D (Xavier Pennec) 4. Eurospeleo 2018 (Stacho Mudrak) ---------------------------------------------------------------------- Message: 1 Date: Tue, 21 Aug 2018 11:06:05 +0100 From: kevin dixon <geospatial3d@gmail.com> To: List for Therion users <therion@speleo.sk> Subject: Re: [Therion] Fix station point using only 2D Message-ID: <CAAUsM+Nn7MgMkKaSMuJJhfVwTvot2RiNcnHdS5+RuP97D_2iAA@mail.gmail.com> Content-Type: text/plain; charset="utf-8" Adam, Radio-location can give you depth but accuracy is not too good. How have your surface positions at the entrance(s) and the radio location been determined ? Professional GNSS (~3cm), DGPS(~1m) or hand held (~3m) ? I have radio-location fixes at the far end of a system to control any accumulated azimuth bias. For these I have assigned an elevation to the radio-location equivalent to the cave survey at the radio location point and used an appropriate SD value for the radio location data. You may have to iterate a few times and experiment with SD values to see how it changes your survey with and without the radio location fix(s). Also better if you have radio location fixes at different points because geology effects the position. Use several in the survey - you should see how they fit (or not) - reject the wildly out ones, adjusting to the rest will help reduce any bias. 150m is a lot of difference so I would be looking at the positional method used, datum and grid, survey instrument calibrations, declination values and then get additional radio locations to confirm. If you are dealing with older survey data then you may want to consider a compass bias - does a survey rotation significantly reduce the difference ? Kevin Dixon On Tue, Aug 21, 2018 at 10:41 AM, Adam Pyka via Therion <therion@speleo.sk> wrote:

Hi all,

How to 'fix' the survey station point (to morph the cave plan) having only 2D coordinates?

Using the radiolocation we get (with quite good accuracy) the station point position which is about 150m beyond the estimated location we get from surveying. So now I wanted to use this position to make a correction to the main polygon. But the 'fix' command need a 3D coords so how should I do that (no, there is no point to measure the depth by radiolocation by some reasons).

Thanks in an advice, Adam _______________________________________________ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion