Author Topic: Error - data not transferring (DistoX / Topodroid)  (Read 2646 times)

Online maxf

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Re: Error - data not transferring (DistoX / Topodroid)
« Reply #25 on: January 04, 2020, 06:55:40 pm »
What you describe Duncan limits your surveying (charitably) to a grade 4b - I can appreciate that after a sump standards have a tendency to drop. It shouldn't be considered a good approach to surveying pre sump.

How so ?

Online alastairgott

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Re: Error - data not transferring (DistoX / Topodroid)
« Reply #26 on: January 04, 2020, 07:29:25 pm »
Quotes from http://bcra.org.uk/surveying/

“Grade 4 (use only if necessary, see note 7)
May be used, if necessary, to describe a survey that fails to attain all the requirements of Grade 5 but is more accurate than a Grade 3 survey.”

Table 2. BCRA gradings for recording cave passage detail

Class A
All passage details based on memory.
Class B
Passage details estimated and recorded in the cave.
Class C
Measurements of detail made at survey stations only.
Class D
Measurements of detail made at survey stations and wherever else needed to show significant changes in passage dimensions.
Notes

The accuracy of the detail should be similar to the accuracy of the line.
Normally only one of the following combinations of survey grades hould be used:
1A,
3B or 3C,
5C or 5D,
6D,
XA, XB, XC or XD.

Online maxf

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Re: Error - data not transferring (DistoX / Topodroid)
« Reply #27 on: January 04, 2020, 07:38:38 pm »
What part of Duncan's methodology grades it as a 4B ? (having surveyed a reasonable amount with him using this method...) he does do splays/ LRUD

Offline Duncan Price

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Re: Error - data not transferring (DistoX / Topodroid)
« Reply #28 on: January 05, 2020, 05:13:59 pm »
What part of Duncan's methodology grades it as a 4B ? (having surveyed a reasonable amount with him using this method...) he does do splays/ LRUD

Splays are taken from every station, not only to define passage cross section at stations but also to pick up changes in passage dimensions between stations.  The grade defines the precision of measurement which is 5 or better and the detail equates to "D" - I'm sure that the late Bryan Ellis would agree with the claimed survey grade.

Offline nearlywhite

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Re: Error - data not transferring (DistoX / Topodroid)
« Reply #29 on: January 05, 2020, 11:19:14 pm »
What part of Duncan's methodology grades it as a 4B ? (having surveyed a reasonable amount with him using this method...) he does do splays/ LRUD

Splays are taken from every station, not only to define passage cross section at stations but also to pick up changes in passage dimensions between stations.  The grade defines the precision of measurement which is 5 or better and the detail equates to "D" - I'm sure that the late Bryan Ellis would agree with the claimed survey grade.

More than happy to be wrong but I doubt what you describe should be a 5D.

How are you putting the detail in? I've assumed the sketch is a rough non centerlined sketch and made to fit afterwards on pocket Topo or equivalent - which is class B. You've recorded detail but not related it directly to the detail when taking the measurements.

The 4 is more the solo effort. Having done a fair bit of solo surveying I've noticed that the accuracy goes down the pan. I doubt that you'd be quite meeting the 5 given the likelihood of:
1) instrument drifting (easily able to lose the 1cm error toleration)
2) missing an off splay due to droplets etc
3) error when transcribing the data later i.e. forgetting what to delete.

This is all compounded due to the tendency when solo surveying not to check loop closure and so we can hide it in the grand survey.

Offline Duncan Price

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Re: Error - data not transferring (DistoX / Topodroid)
« Reply #30 on: January 06, 2020, 08:54:35 am »
More than happy to be wrong but I doubt what you describe should be a 5D.

How are you putting the detail in? I've assumed the sketch is a rough non centerlined sketch and made to fit afterwards on pocket Topo or equivalent - which is class B. You've recorded detail but not related it directly to the detail when taking the measurements.

The 4 is more the solo effort. Having done a fair bit of solo surveying I've noticed that the accuracy goes down the pan. I doubt that you'd be quite meeting the 5 given the likelihood of:
1) instrument drifting (easily able to lose the 1cm error toleration)
2) missing an off splay due to droplets etc
3) error when transcribing the data later i.e. forgetting what to delete.

This is all compounded due to the tendency when solo surveying not to check loop closure and so we can hide it in the grand survey.

Having done survey trips with an assistant using a PDA I haven't noticed any difference in 1 or 2.  3. is down to discipline.  Handwritten notes are taken in the cave which allow the data stored on the PDA to be reconciled to the cave layout.  We're getting off the original topic here anyway.

Offline andrewmc

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Re: Error - data not transferring (DistoX / Topodroid)
« Reply #31 on: January 07, 2020, 09:30:51 am »
Grade 5d surveys, based on nothing more than centrelines, LRUDS, not-to-scale cross-section sketches and not-to-scale rough sketches (fit to the data afterwards), were presumably the norm before the DistoX and PDA approach...

Online alastairgott

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Re: Error - data not transferring (DistoX / Topodroid)
« Reply #32 on: January 07, 2020, 12:53:11 pm »
Hmm, not quite sure about that, I’ve seen some places talking about measuring your arms and useful measuring distances on your body (careful) to measure the distance between parts of the cave.

Ie if a stal is an arm length (approx 1m), then you could draw it in on the square a meter away.

Some people can draw paper surveys and they are inch accurate. If I’m being honest, sometimes I put in my electronic survey and the software alters it. Which shows that just because it’s “modern”, “electric” it doesn’t necessarily mean it is free from error.

What I mean to say is, Duncan probably produces far more accurate surveys than me.

Offline nearlywhite

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Re: Error - data not transferring (DistoX / Topodroid)
« Reply #33 on: January 07, 2020, 06:42:57 pm »
Having done survey trips with an assistant using a PDA I haven't noticed any difference in 1 or 2.

Have you checked? i.e. loop closures? My main reason for asking is I have and was surprised at the increase in error (down to a myriad of factors inc. distoing near scurions etc).

3. is down to discipline.

Provided you take notes of your data and check each disto reading after taking it. All it takes is a couple of errors to ruin a survey... You've not convinced me it's a 5d.

Grade 5d surveys, based on nothing more than centrelines, LRUDS, not-to-scale cross-section sketches and not-to-scale rough sketches (fit to the data afterwards), were presumably the norm before the DistoX and PDA approach...

So those were drawn with a rough plotted centreline, with detail related to it. Which is what it sounds like Duncan's doing anyway. Sketches with no approximated centreline would not fit the BCRA grading, which if you're not reading through the data would be easy to do.

Which shows that just because it’s “modern”, “electric” it doesn’t necessarily mean it is free from error.

True but it's all about reducing the scale of error. Just think how bad you'd be Al if you were surveying 40 years ago  ;D

Online alastairgott

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Re: Error - data not transferring (DistoX / Topodroid)
« Reply #34 on: January 07, 2020, 07:22:54 pm »
I’ve already thought that I could use drag trays as a redimentary measure, so I guess 40 year ago me would be using a needle i’d magnetised and brought into the cave and floated on a pool for the compass bearing, mixed with someone bending their elbow and someone else measuring the angle it makes for the inclination.

And 40year ago me may scrape a grade 3C survey, but would probably get a grade 2C for effort :)

Offline andrewmc

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Re: Error - data not transferring (DistoX / Topodroid)
« Reply #35 on: January 08, 2020, 03:34:27 pm »
http://bcra.org.uk/surveying/
The grade of the survey, as specified by the BCRA rules, has nothing to do with errors/loop closure. A grade 5c survey with a poor loop closure due to a typo is just a bad grade 5c survey with an error.
Most of the number part is to do with the accuracy of the instruments, e.g. bearing and clinometer readings to 1 degree, which an in-calibration DistoX will easily achieve. Length measurements must be done to an accuracy of 1cm but the accuracy of station positions only needs to be within a 10cm sphere so the actual station-to-station length accuracy only needs to be 10cm or so. The way I read it measured LRUDS alone would be sufficient for grade c (estimated LRUDS would get you to grade b only); to get to grade d you need the measured detail between stations (i.e. non-LRUD splays *where required* which might be never in a short simple passage).

Offline nearlywhite

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Re: Error - data not transferring (DistoX / Topodroid)
« Reply #36 on: January 08, 2020, 03:55:31 pm »
I don't have access to the publication in which that summary table is sourced from. Given the UIS definition definitely does have it in, I'm pretty sure I've seen a BCRA publication with it in and that the BCRA probably have updated it since 2002 makes me think it actually is part of the definition.

Here's something from 2011. https://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=1046&context=ijs

I disagree with the point about the D grading - otherwise you're splaying to every stal. It can be a rough approximation to the centreline provided you are actually plotting it.

And the 10cm sphere analogy requires what length leg exactly? Certainly not 2m as you would be hitting the 5% error on distance. So this not really applicable in small featureless passage... I always interpreted that as the acceptable tie in between two surveys.

EDIT: Found it! http://www.chaos.org.uk/survex/cp/CP30/CP30.pdf

It's all a moot point, given that everyone slaps a 5d on every survey anyway.

Offline christine

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Re: Error - data not transferring (DistoX / Topodroid)
« Reply #37 on: January 16, 2020, 07:08:17 pm »
errr...back on topic again...

Thank you Ben for fixing the issue with the Disto (Rich said it was the disto?).

It arrived as I was leaving for work so we'll have a proper play with it when we are back home.

PM us your favourite watering hole and we'll sort some beer for you  :beer2:

Rich said it needed a firmware update? Not got many details...we're in the same (not UK) country but not the same city...we have weird lives...so it might benefit other folk to know what the issue was.

Cheers
Chris

Offline Benfool

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Re: Error - data not transferring (DistoX / Topodroid)
« Reply #38 on: January 16, 2020, 08:49:11 pm »
Yeah it was a problem with the firmware. Took some time to get it to connect to pocket Topo in bootloader mode, then it was reasonably easy to update. Once updated it connected fine to your phone and seemed to all work okay. I'm guessing for some reason the firmware was slightly corrupted, causing the problem.

I think the battery in the phone is a bit knackered though, I'd get a new one if I were you - it's user replaceable (unlike most modern phones!) and should be easy to source on eBay.

No need for payment, just make sure you survey lots of cave with it!

B

 

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