Hi Martin I did try both (survex and therion) before the „correction“. Both did result into the problem. I will check both with correction later. Will post the result then. Cheers, Torsten
> Am 01.11.2018 um 16:27 schrieb Martin Sluka via Therion <[email protected]>: > > Thorsten > > have you try both loop closure methods - Therion’s and Survex’s? > > Martin S. > > >> 1. 11. 2018 v 16:09, Torsten Schnitter via Therion <[email protected]>: >> >> Hi >> >> I figuered out the problem and may be there is a bug in loop closure... or >> somewhere else. >> >> The cave does start at 0m of depth and with a fixed point (fix 0 x y z) with >> z=118.4m. >> After roughly 800m of underwater cave survey (which does result in absolute >> z values for every station) the cave does surface again at a depth of 0m. >> I fixed this point as well (fix 0 x y z) with z=118.4m (to correct the x and >> y error). >> >> So far so good. >> But further (around 1km more) into the cave it does surface again and I >> realized in elevation view that 0m is not at the same level than the first >> two points are. >> As soon as I deleted one of the two fixed points the z elevation was as >> expected and the 0m point into the cave was at the same level than the first >> two surface points. >> >> After some tests I realized the start of the cave was the problem. >> You can see this part on the attached picture. >> As you can see there is a vertical start of the cave. >> >> Here the data from that first part: >> data diving station depth newline tape compass >> 0 0.0 >> 4.9 0 >> 1 4.9 >> 9.1 0 >> 2 14.0 >> 28.1 78 >> 3 28.2 >> 8.9 88 >> 4 30.3 >> >> As soon as I add 0.01m to the first and second (vertical) tape measurement >> (4.9 = 4.91 and 9.1 = 9.11) all is good and the problem with loopclosure is >> gone. Both fixed points are added again and the eleveation is as expected >> (0m level is at the same level at all points). >> So there is some more distance needed for the vertical parts. But I can't >> explain why. >> >> Is this a problem with the loop closure algorithm? >> May be some of the experts around can post a explanation for this behaviour!? >> >> regards, >> Torsten >> >>> Bruce Mutton via Therion <[email protected]> hat am 30. Oktober 2018 um >>> 08:34 geschrieben: >>> >>> Torsten >>> >>> The image of the xvi file makes it look as though there is a loop (not sure >>> if it is a plan or elevation view – presume it is elevation). Also if you >>> have a fixed point at each end, then this could also cause ‘a loop’ which >>> might give differing elevations at each end. >>> >>> Also, if the water is flowing, then the water levels at each end will >>> actually differ. >>> >>> >>> But I assume you have correctly assessed these effects as negligible, or at >>> least not detected by your survey method. >>> >>> >>> I think you are implying that the 0m line is a raster background. If that >>> is the case, it may be distorted by Therion. One way to check would be to >>> turn on gridlines for the layout. That will show you what Therion really >>> thinks is a horizontal line. >>> >>> >>> Also check that Therion has the water surface survey stations at the same >>> altitude. You can check this easily by interrogating a .3d output with >>> Aven. >>> >>> >>> Bruce >>> >>> >>> From: Therion <[email protected]> On Behalf Of Torsten Schnitter >>> via Therion >>> Sent: Tuesday, 30 October 2018 04:36 >>> To: [email protected] >>> Cc: Torsten Schnitter <[email protected]> >>> Subject: [Therion] ***UNCHECKED*** Problem with elevation view >>> >>> >>> Hi all >>> >>> I have a under water cave survey and all the data is done with depth >>> measurements. >>> So the Z coordinates are absolute and the survey is not with clino data. >>> The cave starts at one point and after roughly 800m you have another >>> surface point. >>> >>> When I compile the data I get a strange behaviour. >>> Although it's not a WYSIWIG map editor I would expect points which have the >>> same depth are at the same "depth"/level on the xvi file. But they are not >>> (see attached screenshot "elevation problem"). >>> The 2 points within the red marks do have the same depth measurements. >>> But if you have a closer look to it you can see they are not at the same >>> level. >>> (They differ somehow in x/y way and therefore the points are not on top of >>> each other.) >>> There are no loop closures inbetween which could be a reason for different >>> levels. >>> >>> Not having the same level with these points (I assume it is this point) >>> leads to a bigger problem later on. >>> When drawing the elevation scraps and putting a water surface (depth = 0m) >>> to the scraps and having a raster in the background, the surface at the >>> beginning of the cave is not at the same level than at the next surface >>> point of the cave. But it should be. >>> See pictures "elevation problem-start" and "elevation problem-end". >>> >>> What's wrong? >>> Can anybody help? >>> If more info is needed please let me know. >>> >>> Thanks, >>> Torsten >>> >> >> >> >>> _______________________________________________ >>> Therion mailing list >>> [email protected] >>> https://mailman.speleo.sk/listinfo/therion >> >> >> >> <Entrance-1.JPG>_______________________________________________ >> Therion mailing list >> [email protected] >> https://mailman.speleo.sk/listinfo/therion > > _______________________________________________ > Therion mailing list > [email protected] > https://mailman.speleo.sk/listinfo/therion
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