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
