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
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 <therion-bounces@speleo.sk> On Behalf Of Torsten Schnitter via Therion Sent: Tuesday, 30 October 2018 04:36 To: therion@speleo.sk Cc: Torsten Schnitter <torsten.schnitter@netcologne.de> 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
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 <therion@speleo.sk> 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 <therion-bounces@speleo.sk> On Behalf Of Torsten Schnitter via Therion Sent: Tuesday, 30 October 2018 04:36 To: therion@speleo.sk Cc: Torsten Schnitter <torsten.schnitter@netcologne.de> 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
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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 <therion@speleo.sk>:
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 <therion@speleo.sk> 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 <therion-bounces@speleo.sk> On Behalf Of Torsten Schnitter via Therion Sent: Tuesday, 30 October 2018 04:36 To: therion@speleo.sk Cc: Torsten Schnitter <torsten.schnitter@netcologne.de> 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
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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 <therion@speleo.sk>:
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 <therion@speleo.sk>:
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 <therion@speleo.sk> 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 <therion-bounces@speleo.sk> On Behalf Of Torsten Schnitter via Therion Sent: Tuesday, 30 October 2018 04:36 To: therion@speleo.sk Cc: Torsten Schnitter <torsten.schnitter@netcologne.de> 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 Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
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_______________________________________________ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
Hi Martin I tried both loop closure methods. Survex and Therion. It doesn't make any difference. With both it's not at one level without the extra 0,01m for vertical shots. Both are correct with the extra for the shots. hth, Torsten
Martin Sluka via Therion <therion@speleo.sk> hat am 1. November 2018 um 16:27 geschrieben:
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 < therion@speleo.sk mailto:therion@speleo.sk >:
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 < therion@speleo.sk mailto:therion@speleo.sk > 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 <therion-bounces@speleo.sk mailto:therion-bounces@speleo.sk > On Behalf Of Torsten Schnitter via Therion Sent: Tuesday, 30 October 2018 04:36 To: therion@speleo.sk mailto:therion@speleo.sk Cc: Torsten Schnitter <torsten.schnitter@netcologne.de mailto:torsten.schnitter@netcologne.de > 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
> >
> > > _______________________________________________
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> >
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>
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Hi Concerning the loop closure problem I observed some more points. Following is the set: A underwater cave with a GPS position at the start and at the water surface (0m). Inbetween there is a second surface point with also a GPS position at the water surface (0m). Then there is a second start of survey from inside the cave. We have a GPS position of one point inside the cave (done with radio location). Both surveys should come together at one point of course. Due to underwater survey the x and y coordinates (compass) is not that accurate and the two final points do not match exactly (of course not). In picture "Cave-Lake-without-loop-closed-plan-view" you can see the plan view from this two points which are not at the same place (as expected). In picture "Cave-Lake-without-loop-closed-elevation-view" you can see the elevation view from this two points. May be it's hard to see but both points are at the exact same level (which they should be). (I draw a small scrap - red line - to show the water level (at correct level 0m) before the loop closure.) After the loop closure I get some problems. On the picture "Cave-Lake-with-loop-closed-plan-view" you can see the loop closed and corrected in x and y orientation. This seems to be ok (no problem with that). On the picture "Cave-Lake-with-loop-closed-elevation-view" you can see the elevation view after loop closure (it doesn't make any difference using therion or survex as loop closure algorithm). You can see the water level is not at the 0m level (scrap line) anymore, it's far below that. The loop closure corrected the survey also in z orientation although the two "end" points have been at the same level before and no correction should have been necessary. Due to this corrections the "lake" inside the cave is not flat anymore but it is bend somehow (high at beginning, lower in the middle and high up again at the end). I assume everybody does agree it's not possible to have a lake with bended surface. ;-) Due to this corrections I observed another point as well. Having a vertical shot before the loop closures (and for sure this is vertical!) this shot is not vertical anymore after the loop closures. In my opinion there are two points: - Having corrections in x and y with loop closures doesn't mean implicitly there is also a correlating correction to the z axis. Especially if the points are at the same level already. - With loop closure there should be a special treatment with vertical shots (in x/y orientation) and with horizontal shots (in z orientation). May be there should be no correction due to loop closures!? What do you think? Btw: does anybody have a solution for my problem: No correction in z orientation for this loop closure? regards, Torsten
Torsten Schnitter via Therion <therion@speleo.sk> hat am 1. November 2018 um 21:23 geschrieben:
Hi Martin
I tried both loop closure methods. Survex and Therion. It doesn't make any difference.
With both it's not at one level without the extra 0,01m for vertical shots. Both are correct with the extra for the shots.
hth, Torsten
> > Martin Sluka via Therion <therion@speleo.sk> hat am 1. November 2018 um 16:27 geschrieben:
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 < therion@speleo.sk mailto:therion@speleo.sk >:
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 < therion@speleo.sk mailto:therion@speleo.sk > 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 <therion-bounces@speleo.sk mailto:therion-bounces@speleo.sk > On Behalf Of Torsten Schnitter via Therion Sent: Tuesday, 30 October 2018 04:36 To: therion@speleo.sk mailto:therion@speleo.sk Cc: Torsten Schnitter <torsten.schnitter@netcologne.de mailto:torsten.schnitter@netcologne.de > 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 Therion@speleo.sk mailto:Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
> > >
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> >
>
> > _______________________________________________
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Torsten, What about the inclination, is’t it this the problem of horizontal misplacement? Check the „extend vertical“ command of centerline section in Thbook - it solves the problem with vertical shots they should be vertical after loop-closure. If you draw scrap with water area, there is the parameter of line "adjust horizontal/vertical“ for line point. It will align the line point with the previous one, so the water level should be horizontal. Martin S.
3. 11. 2018 v 11:30, Torsten Schnitter via Therion <therion@speleo.sk>:
Hi
Concerning the loop closure problem I observed some more points.
Following is the set: A underwater cave with a GPS position at the start and at the water surface (0m). Inbetween there is a second surface point with also a GPS position at the water surface (0m). Then there is a second start of survey from inside the cave. We have a GPS position of one point inside the cave (done with radio location). Both surveys should come together at one point of course. Due to underwater survey the x and y coordinates (compass) is not that accurate and the two final points do not match exactly (of course not).
In picture "Cave-Lake-without-loop-closed-plan-view" you can see the plan view from this two points which are not at the same place (as expected). In picture "Cave-Lake-without-loop-closed-elevation-view" you can see the elevation view from this two points. May be it's hard to see but both points are at the exact same level (which they should be).
(I draw a small scrap - red line - to show the water level (at correct level 0m) before the loop closure.)
After the loop closure I get some problems. On the picture "Cave-Lake-with-loop-closed-plan-view" you can see the loop closed and corrected in x and y orientation. This seems to be ok (no problem with that). On the picture "Cave-Lake-with-loop-closed-elevation-view" you can see the elevation view after loop closure (it doesn't make any difference using therion or survex as loop closure algorithm). You can see the water level is not at the 0m level (scrap line) anymore, it's far below that. The loop closure corrected the survey also in z orientation although the two "end" points have been at the same level before and no correction should have been necessary.
Due to this corrections the "lake" inside the cave is not flat anymore but it is bend somehow (high at beginning, lower in the middle and high up again at the end). I assume everybody does agree it's not possible to have a lake with bended surface. ;-)
Due to this corrections I observed another point as well. Having a vertical shot before the loop closures (and for sure this is vertical!) this shot is not vertical anymore after the loop closures.
In my opinion there are two points: - Having corrections in x and y with loop closures doesn't mean implicitly there is also a correlating correction to the z axis. Especially if the points are at the same level already. - With loop closure there should be a special treatment with vertical shots (in x/y orientation) and with horizontal shots (in z orientation). May be there should be no correction due to loop closures!?
What do you think?
Btw: does anybody have a solution for my problem: No correction in z orientation for this loop closure?
regards, Torsten
Torsten Schnitter via Therion <therion@speleo.sk> hat am 1. November 2018 um 21:23 geschrieben:
Hi Martin
I tried both loop closure methods. Survex and Therion. It doesn't make any difference.
With both it's not at one level without the extra 0,01m for vertical shots. Both are correct with the extra for the shots.
hth, Torsten
Martin Sluka via Therion <therion@speleo.sk> hat am 1. November 2018 um 16:27 geschrieben:
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 < therion@speleo.sk <mailto:therion@speleo.sk>>:
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 < therion@speleo.sk <mailto:therion@speleo.sk>> 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 <therion-bounces@speleo.sk <mailto:therion-bounces@speleo.sk>> On Behalf Of Torsten Schnitter via Therion Sent: Tuesday, 30 October 2018 04:36 To: therion@speleo.sk <mailto:therion@speleo.sk> Cc: Torsten Schnitter <torsten.schnitter@netcologne.de <mailto:torsten.schnitter@netcologne.de>> 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
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3. 11. 2018 v 11:30, Torsten Schnitter via Therion <therion@speleo.sk>:
Due to this corrections I observed another point as well. Having a vertical shot before the loop closures (and for sure this is vertical!) this shot is not vertical anymore after the loop closures.
One thing more: • infer <what> <on/off> ▷ ‘infer plumbs on’ tells the program to interpret gradients °æ90 ◦ as UP/DOWN (this means no clino corrections are applied). ‘infer equates on’ will case program to interpret shots with 0 length as equate commands (which means that no tape corrections are applied) Martin S.
Hi Martin Thanks a lot for your hints. Espacially the infer command (I didn't know this). While playing around with this command I recognized no change in behaviour to vertical shots. Of course this could not be and something else was wrong. In the end I realized that all lines in the Therion .ini file where with comments. Of course therefore it didn't make any difference in changing loop closure method from survex to therion and vice versa. I'm using a windows with Therion and if you have a look to the ini file there are missing all line feeds. Therefore this ini-file is not that readable... anyhow. I build this file new with command "therion.exe --print-init-file" and all line feeds where in place. Than I realized my mistake and uncomment the line with loop closure method. And now I have to say: there IS a difference in the effects using loop closure method survex or therion. With 'survex' you get the problems I observed (0m beeing not at the same level and other misplacements). But with 'therion' as the loop closure method it worked very good and I got all 0m lines at the same level. But some minor misplacements nevertheless. And with the command 'infer plumbs on' it looks pretty perfect. Vertical shots stay vertical and after loop closures as well. Hopefully my problems with the elevation view are solved now... I have to check some more details but it's looking pretty good. Thanks again for all the help and sorry for my confusion with the loop closure method. regards, Torsten
Martin Sluka via Therion <therion@speleo.sk> hat am 3. November 2018 um 12:44 geschrieben:
> > 3. 11. 2018 v 11:30, Torsten Schnitter via Therion < therion@speleo.sk mailto:therion@speleo.sk >:
Due to this corrections I observed another point as well. Having a vertical shot before the loop closures (and for sure this is vertical!) this shot is not vertical anymore after the loop closures.
>
One thing more:
• infer <what> <on/off> ▷ ‘ infer plumbs on ’ tells the program to interpret gradients °æ 90 ◦ as UP/DOWN (this means no clino corrections are applied). ‘ infer equates on ’ will case program to interpret shots with 0 length as equate commands (which means that no tape corrections are applied)
Martin S.
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participants (4)
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Bruce Mutton -
Martin Sluka -
Martin Sluka -
Torsten Schnitter