Author Topic: DistoX  (Read 4331 times)

Offline alasdair neill

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DistoX
« on: August 21, 2009, 11:46:34 am »
Hopefully someone more involved can add to the following, but checks on several DistoX's just made in Matienzo showed that following an east-west line then reversing along a back bearing failed to give the expected 180 degrees difference - errors of 5 degrees were come up with. It seems the calibration procedure may need clarification.

Regarding the use of DX'S and PDA's I found as being a member of a surveying team very annoying - surely part of the needs of surveying is to get maximum involvement for everyone. I totally understand someone who has splashed out on the two devices wanting to do the work themselves, but it leaves everyone else twiddling their thumbs, and the resulting drawings from the PDA although probably more accurate as to passage outline, tended to lack passage detail.

On some trips we came up with a compromise where someone else was drawing in passage detail the luddite way with a pencil and notebook.

Offline Rob

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Re: DistoX
« Reply #1 on: August 21, 2009, 12:01:28 pm »
Regarding the use of DX'S and PDA's I found as being a member of a surveying team very annoying - surely part of the needs of surveying is to get maximum involvement for everyone. I totally understand someone who has splashed out on the two devices wanting to do the work themselves, but it leaves everyone else twiddling their thumbs, and the resulting drawings from the PDA although probably more accurate as to passage outline, tended to lack passage detail.
This summer in Crete we had teams of three. For the horizontal stuff we had:
  • one person in front exploring and picking/marking stations
  • second person with DistoX firering forward legs and passage detail
  • last person at the back with PDA drawing around the already received lines as he went
For certain bits of the cave this was unbelievably quick!
The end is where we start....

Offline Jams

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Re: DistoX
« Reply #2 on: August 21, 2009, 01:09:42 pm »
Takes too long doing it all on your own.

We were using the same setup as Rob, works very well. Drew rough passage detail while surveying and neated it up later. When correctly calibrated, it should be easier to get greater accuracy.

Offline biffa

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Re: DistoX
« Reply #3 on: August 21, 2009, 06:22:15 pm »
It seems the calibration procedure may need clarification.

Found mine to be scarily accurate and whilst leap frogging managed to close loops with errors from 0.08-0.98% over loops as large as 400m whilst surveying in horrible rifty stuff.  Do you know what value of calibration 'goodness' you got whilst calibrating (the third value given in bottom of screen when you click evaluate- manual says it should be less than 0.5 - above closures done with ~0.3).

Thought the Matienzo DistoX was working fine whilst I was out there, did you speak to Juan about it?  The calibration manual seems quite clear?

Offline menacer

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Re: DistoX
« Reply #4 on: August 21, 2009, 07:47:05 pm »
Hi Ali.  LOL I remember THAT trip  ;)
This  particular  Distox had apparently worked flawlessly on a previous seasons caving apparently with data with very similar readings. On this particular trip however, it wasnt, and the readings were varying upto 7 or 8 degrees as well as the distance saying 2m when it was more like 4m, we were wondering which readings to believe or not.

Ive found similar things with the SAP, for whatever reason they can just go out of calibration between trips.Im starting to think these electronic gadgets do need a little more "above ground nurse mading" to be thoroughly effective when underground.

The new SAP field calibration is brilliant for sorting this out. If prior to a trip you find its out (by doing a fixed point on all four rotations of the device) you can do a quick field calibration and away you go.

It seems you really need to be a geek with your equipment before a trip in order for it to work effectively on a trip (even charge it properly like I forgot to once  :-[ ) because if you find yourself on a survey trip where  the readings are duff, and then the bluetooth packs up, and then it works again, but the reading are weird, and then it need all packing away agin to walk 5m down the passage to be unpacked again, and then the pda isnt working, oh but it is again, but now the reading are weird, well you get what im saying....

at least pencil and paper arnt that fickle, stuff it down yer oversuit jobs a goodun..







Chaos, panic, and disorder - my work here is done.

Online SamT

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Re: DistoX
« Reply #5 on: August 21, 2009, 08:18:54 pm »
Quote
because if you find yourself on a survey trip where  the readings are duff, and then the bluetooth packs up, and then it works again, but the reading are weird, and then it need all packing away agin to walk 5m down the passage to be unpacked again, and then the pda isnt working, oh but it is again, but now the reading are weird, well you get what im saying....

at least pencil and paper arnt that fickle, stuff it down yer oversuit jobs a goodun..

Thats been my reticence so far.

I've gone for it in the end, The eldon have got an X, and my ebay PDA just arrived in the post this week (no end of faffing about with it TBH).

I'm still nervous about doing a proper full on survey (I need to do a couple in baggers). If it does all go to cock underground, its gonna have to be one hell of an otterbox to prevent the thing being smashed to smithereens out of frustration. I fully intend taking the suunto's and a note book as backup.

I know everyone belts on about the accuracy, but I've found that people trust them implicitly, and because its so quick to cover ground, and all the data transfer happens automatically - errors are not going to be noticed.

Mark my words, one day, some sort of huge surveying 'gaff' is going to be realised, due to a DistoX or equivalent giving out dicky readings. (of course this does happen with compasses too, like the story I heard about the guy who used his ammo can to rest his compass on for sighting in some low stuff. Funnily enough, his survey didn't really make sense.

Oh well, managed to get one calibrated today after several attempts, the worst being when my PDA completely ran out of batteries just after I'd hit evaluate, and it seemed to do a hard reset. Lost all the data.  :furious:


Offline alasdair neill

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Re: DistoX
« Reply #6 on: August 22, 2009, 11:41:25 am »
Regarding calibration, this needs someone else to report as I was not involved, just reported what was said at the time.
Whilst a DistoX, or SAP, will doubtless give better loop closures than using traditional compass/clino, is this the same with closures between say entrances with known positions? According to the calibration manual "a calibrated reference stretch is not needed".

Can you claim BCRA grade 5 without calibration against known points?. The traditional method of calibration - against distant points of known position at surface - is probably not workable but presumably a Disto X could be compared with a compass calibrated by that method. Do users do this?

Rob's teams of three sounds fine, if only everyone worked that way.

Offline Juan

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Re: DistoX
« Reply #7 on: August 23, 2009, 08:35:31 am »
Teams of 2 work well, at least in smaller passages or maze-type caves.
  • Person at the back fires the survey leg, and passes the DistoX to the front person who is exploring and marking the next station
  • Front person fires the LRUD and any other splays while back person draws up passage detail and section.
  • Front person collects DistoX as back person moves off to next station.
This obviously also involves all trip members.

Offline Katie

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Re: DistoX
« Reply #8 on: August 23, 2009, 11:39:40 am »
Teams of 2 work well, at least in smaller passages or maze-type caves.
  • Person at the back fires the survey leg, and passes the DistoX to the front person who is exploring and marking the next station
  • Front person fires the LRUD and any other splays while back person draws up passage detail and section.
  • Front person collects DistoX as back person moves off to next station.
This obviously also involves all trip members.

Interesting setup. We did something similar when in teams of 2, but without needing to swap the DistoX between us:
  • Person in front marks survey station, backfires to the previous station (which is illuminated by the person behind) then does the LRUDs and moves on.
  • Person behind has PDA and draws up passage detail as they go.

Offline Juan

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Re: DistoX
« Reply #9 on: August 24, 2009, 09:21:14 am »
Quote
•Person at the back fires the survey leg, and passes the DistoX to the front person who is exploring and marking the next station
•Front person fires the LRUD and any other splays while back person draws up passage detail and section.
•Front person collects DistoX as back person moves off to next station.
Quote
Interesting setup.

Possibly "interesting" because it was wrong.  :spank:
Method should read
•Person at the back fires the survey leg, and passes the DistoX to the front person who is exploring and marking the next station
•Front person fires the LRUD and any other splays while back person draws up passage detail and section.
•Back person collects DistoX as front person moves off to next station.

Bat girl's method appears a "better" method, but all ways depend on the passage(s) and the team expertise. It's also perfectly feasible for one person to survey smaller passages. (But may be unacceptable for safety reasons).

Offline sluka

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Re: DistoX
« Reply #10 on: August 24, 2009, 09:50:54 am »
Bat girl's method appears a "better" method, but all ways depend on the passage(s) and the team expertise. It's also perfectly feasible for one person to survey smaller passages. (But may be unacceptable for safety reasons).

To measure only LRUD misses the main advantage of DistoX+PocketTopo combo - splay shots. I prefer if the sketcher measures splay shots and draws too, because in other alternatives it is quite difficult to recognize which splay shot in PocketTopo is which. No problem in simple tube gallery, but in complicated rooms it could be big problem.

Offline footleg

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Re: DistoX
« Reply #11 on: August 24, 2009, 10:47:15 am »
but presumably a Disto X could be compared with a compass calibrated by that method. Do users do this?

Yes, this is exactly what I do to check that the DistoX is still well calibrated. There is a real tendency to trust digital read outs implicitly because they give you an easy to read number. But you have to check that this number is correct in the first place!

I have not yet managed a survey between two entrances with a DistoX to compare the loop closed between 'fixed' GPS points. But that would be a good confirmation of the survey accuracy compared to 'traditional' methods (provided the GPS fixes were also accurate).

Online Cave_Troll

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Re: DistoX
« Reply #12 on: August 24, 2009, 11:11:06 am »
i suspect that errors in GPS of +/- 5m on each entrance could lead to a bigger error than the disto

Offline Joel Corrigan

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Re: DistoX
« Reply #13 on: September 01, 2009, 12:30:27 pm »
We had a DistoX in the Dachstein and came to the following conclusion: if you haven't got a background with standard surveying methods you probably won't even notice/consider errors.  We had to redo a good few legs as the clino/compass started going loopy.  We found that turning it off and on again seemed to sort it out for a while.  Great bit of kit (especially in caves that are 2 degrees), tricky to hold steady for long shots, brilliant in meanders and crawls, but you really do need your wits about you.  We were doing traditional note-taking and sketches as we were too lazy to get the PDA sorted.....