Re: [Therion] Radiolocation Fixed Points
On 25/08/2022 20:16, Tarquin Wilton-Jones--- via Therion wrote: >> I am only suggesting removing one of the radiolocation points because >> your siphon survey sounds like it's fairly accurate, and as tarquin says >> not likely to be causing the error. I would think the accuracy of the >> radiolocation could be the weak link, but i'm no expert with radiolocation. > > Depends. I would say something that uses gyroscopes to detect its > position, is likely to be quite inaccurate, but that really depends on > the quality of the device. I know Andrew has worked with some supremely > accurate devices, but in this case, I would consider it quite suspect. Did some more looking into it. The manufacturers do not state the accuracy of their inertial sensors (gyroscopes and accelerometers). This is a summary of what I found: This particular one works using GPS when in contact with the surface, then gyroscopes, accelerometers, compass and depth gauge underground or underwater. Its design seems to be aimed at the use of scooters, rather than being handheld. The compass has only 3-5° accuracy (unless specifically calibrated), and the depth gauge has 0.3m accuracy. Part of its operation uses a speed sensor which detects water flow, so its results vary depending on the current within the cave, and its accuracy is 2% when moving at scooter speed (and likely far worse at slow speeds). The main accuracy limitation is the quality of the inertial sensors, which will become progressively worse over time, so the accuracy decays over longer dives. Even a high quality device is expected to lose 50 m of accuracy within 15 minutes, and a poor one within just 10 seconds [taken from a forum thread about this exact problem with this device]. The manufacturer does not state the quality of the sensors or their use of them. The equivalent cave surveying grade is therefore very hard to estimate, and probably equates to grade 2 at best. It would be interesting to know how well the device actually performs in a test without GPS, comparing a disto survey with an underwater dive survey done using an ENC3. ___ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
Re: [Therion] Radiolocation Fixed Points
> I am only suggesting removing one of the radiolocation points because > your siphon survey sounds like it's fairly accurate, and as tarquin says > not likely to be causing the error. I would think the accuracy of the > radiolocation could be the weak link, but i'm no expert with radiolocation. Depends. I would say something that uses gyroscopes to detect its position, is likely to be quite inaccurate, but that really depends on the quality of the device. I know Andrew has worked with some supremely accurate devices, but in this case, I would consider it quite suspect. From the specs, it sounds like roughly grade 2 compass (5°), reasonably accurate depth (30 cm), but using gyroscope and accelerometer to measure motion is not exactly accurate, at least in most consumer grade equipment. But I would love to hear otherwise! If you set the "sd" options correctly for the device, and set the appropriate standard deviations for the radio location fixes, then Therion should be able to sort out the error distribution accordingly. sd for a radio location is likely to be quite large, but actually not as bad as you might expect. Radio location "may be able to locate the horizontal position of an underground point to within just 1.5% of the depth below ground (about 1 metre per 67 metres of depth), and the depth to about 5% of its actual depth, depending on how level the surface is". But that is in addition to whatever error there is in locating the point on the surface where the radio location antenna was used (ie. if you survey to it at grade 5, or locate it with a GPS that has a 5x5x15 m error - fairly good for a GPS, no matter what yours might like to claim). Both of those errors would need to be put into the standard deviation, to get it right. eg. for a passage 200 m below surface: 1.5% * 200 = 3 5% * 200 = 10 3 + 5 = 8 10 + 15 = 25 fix sumpstart 123 123 123 8 8 25 # 8 m easting, 8 m northing, 25 m alt ___ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
Re: [Therion] Radiolocation Fixed Points
HI Daniel, We had a similar problem on a mine called Speedwell in the UK. Our problem, we found out, was that we had very few points in a straight line of passage leading to a middle entrance of the system. The model we were using had quite long lengths for this part of the survey, so when therion was trying to distribute errors across the whole survey, the least accurate part of the survey it decided was this straight bit of passage. so there was some big distortions. I would ask whether you have entrances or other radio location points on both sides of the siphon. If the radiolocation for one of the sides of the siphon is not accurate then including both radiolocation points could introduce distortion. I would consider not using the radiolocation point on the "entrance" side of the siphon. or if the distance between the entrance and the entrance side of the siphon is small in comparison to the cave, then keeping the radiolocation here and removing the radiolocation on the far side of the siphon. Say your model is: Entrance Grid ref (accurate) ~some normal cave survey (really accurate) *. radiolocation of entrance side of siphon (possibility for error?)* ~siphon survey (really accurate) radiolocation of far end of siphon (possibility for error?) ~some more dry cave survey (really accurate) second entrance (accurate) or distant third radiolocation point. (possibility for error?) I am only suggesting removing one of the radiolocation points because your siphon survey sounds like it's fairly accurate, and as tarquin says not likely to be causing the error. I would think the accuracy of the radiolocation could be the weak link, but i'm no expert with radiolocation. Alastair. On Thu, 25 Aug 2022 at 07:51, Daniel Chailloux wrote: > Hi, > > > > We are facing a problem with Therion and fixed points obtained by > radiolocation. > > This is the survey of a very long siphon taken with the SeaCraft ENC3 tool. > > There are many many stations saved automatically with the device. > > We fixed two points determined by radiolocation, one at the beginning of > the siphon and another at the end. > > When after Therion compilatione, the survey is completely distorted. > > Doesn't the problem come from too many shots and Therion not being able to > compensate for the very small shots? > > > > Have you encountered this problem before? > > > > Thanks for your help, > > -- > > Daniel Chailloux. > > _ > > *Daniel Chailloux* > > 17, avenue Gabrielle d’Estrées > > 91830 Le Coudray-Montceaux - France > > Mobile : +33 6 8290 7375 > > Email : danielchaill...@orange.fr > > > ___ > Therion mailing list > Therion@speleo.sk > https://mailman.speleo.sk/listinfo/therion > ___ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
Re: [Therion] Radiolocation Fixed Points
> Therion in general seems to work at the 1 cm level when exporting > certain formats, but I think (someone correct me if I am wrong) that > internally, it works on much higher resolution, and therefore can work > even with tiny legs. I tested this, and can confirm that Therion can indeed work at tiny, tiny leg lengths. I produced a survey of 100'000 legs, of 1 mm length. (I tried 1 million, but Loch just crashed!). And then at 0.1 mm length It is below the resolution of the Loch graphics handling to render each of the tiny lines correctly at that scale, but the overall rendering is correct. When fixing the points at the start and end of the survey, the overall rendering is still correct, and the error is distributed correctly. So basically, Therion can work at crazy small leg lengths, it does not cause strange distortions. But that can take it beyond the capabilities of the app being used to render the output. Your error probably lies elsewhere. ___ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
Re: [Therion] filtering for export continuation-list
Like this https://therion.speleo.sk/wiki/drawingchecklist#points and scroll down to point continuation -text "Description" -attr who "M Name" -attr what climb -attr priority low -attr ref plan # -explored 8.0m 'who' is the person(s) who identified the the item, or the person assigned to resolve the issue. 'what' can be rift|climb|pitch|squeeze|tight|sump|rock-pile or whatever you like. (I'm thinking of using it as a 'to do' list so I could add, for example survey|re-rig) 'priority' can be any number, text phrase or be omitted, 'ref' is intended to indicate where the data entry to this point is made, ie plan|elev|centreline, where = ext for extended elevation, or, say 090 for the direction of a projected elevation, or centreline if it is in the .th file (Therion does not yet report the location of this information, so manually entering it helps down the track when you want to make edits and updates). For more explanation follow the link. Bruce From: Therion On Behalf Of A Gott Sent: Thursday, 25 August 2022 08:11 To: List for Therion users Subject: [Therion] filtering for export continuation-list HI Therion friends, A friend posed an interesting question on a data set we hold in Therion. We have entered a lot of leads (point continuation's) in both elevation and plan th2 files. we have come to export these and have found that they are both coming out together, with neither being an exact copy of each other it's hard to tell them apart. Is there any way you can filter the "export continuation-list" to only output plan continuations? At present for a workaround, I have suggested exporting to .txt and copy and pasting into excel, so that the list can be filtered. is it possible to filter prior to export? (if not, would it be possible to include an extra column on the export to show which projection the continuation was noted in, eg. plan, extended, elevation [90] - so this can then be filtered in excel/a database). I note that even when using a select from the map structure, therion still defaults to looking at the full .th dataset. Regards, Alastair Gott. ___ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
Re: [Therion] Radiolocation Fixed Points
Hi Daniel I had the same problem with my survey. I can't remember if it only was this one thing but I had to add following line into centerline data: infer plumbs on You can give it a try. ;-) regards, Torsten > Daniel Chailloux hat am 25.08.2022 08:51 CEST > geschrieben: > > > > Hi, > > > > We are facing a problem with Therion and fixed points obtained by > radiolocation. > > This is the survey of a very long siphon taken with the SeaCraft ENC3 tool. > > There are many many stations saved automatically with the device. > > We fixed two points determined by radiolocation, one at the beginning of the > siphon and another at the end. > > When after Therion compilatione, the survey is completely distorted. > > Doesn't the problem come from too many shots and Therion not being able to > compensate for the very small shots? > > > > Have you encountered this problem before? > > > > Thanks for your help, > > -- > > Daniel Chailloux. > > _ > > Daniel Chailloux > > 17, avenue Gabrielle d’Estrées > > 91830 Le Coudray-Montceaux - France > > Mobile : +33 6 8290 7375 > > Email : danielchaill...@orange.fr mailto:danielchaill...@orange.fr > > > > ___ > Therion mailing list > Therion@speleo.sk > https://mailman.speleo.sk/listinfo/therion > ___ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
Re: [Therion] Radiolocation Fixed Points
Hi Daniel, > There are many many stations saved automatically with the device. > > We fixed two points determined by radiolocation, one at the beginning of > the siphon and another at the end. Interesting. How are you fixing only the easting and northing, without fixing the altitude? (Or are you fixing the altitude, with a high standard deviation factor?) > When after Therion compilatione, the survey is completely distorted. It would help to see an example of this - source code for the survey itself. (Only the part with the siphon and fixed points.) Also, what happens if you break the data for the siphon by disconnecting two stations from each other; do the two ends end up where you expect them to be? > Doesn't the problem come from too many shots and Therion not being able > to compensate for the very small shots? Therion in general seems to work at the 1 cm level when exporting certain formats, but I think (someone correct me if I am wrong) that internally, it works on much higher resolution, and therefore can work even with tiny legs. Cheers, Tarquin ___ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
[Therion] Radiolocation Fixed Points
Hi, We are facing a problem with Therion and fixed points obtained by radiolocation. This is the survey of a very long siphon taken with the SeaCraft ENC3 tool. There are many many stations saved automatically with the device. We fixed two points determined by radiolocation, one at the beginning of the siphon and another at the end. When after Therion compilatione, the survey is completely distorted. Doesn't the problem come from too many shots and Therion not being able to compensate for the very small shots? Have you encountered this problem before? Thanks for your help, -- Daniel Chailloux. _ Daniel Chailloux 17, avenue Gabrielle d’Estrées 91830 Le Coudray-Montceaux - France Mobile : +33 6 8290 7375 Email : danielchaill...@orange.fr ___ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
