Surveying large passage for the first time

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Surveying large passage for the first time

Postby GroundquestMSA » Sep 9, 2012 8:25 pm

I've an upcoming survey project in a short (<3000ft.) cave that features 700 +/- ft. of big passage (50-100' wide, 15-40' high). This is quite a switch from the tiny stuff I've done so far so I'm looking for any general tips or cautions that apply to surveying and sketching in these conditions.
Thanks folks.
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Re: Surveying large passage for the first time

Postby Chads93GT » Sep 9, 2012 8:42 pm

I just started using larger survey paper than the standard 5x7" sheets. I wish I would have used this paper in our large project which as passage up to 40' high and 50' wide. Thats a tip.......
Pick and choose your features, just like any survey.

If you don't already use one, buy a disto. Even a $100 stanley laser disto from home depot is better than nothing and it will improve the quality of your map.

Leave the tape on the ground after the distance is measured.
As you sketch the line plot on the paper, put a small hash ever 10' on the line, and every 10' on the tape measure, shoot your laser disto to the walls and features. This will greatly improve the accuracy of the map. Sure you could eyeball it, but shooting with a disto is just as easy and more accurate.

you can slice up a zip lock bag and tape it around the disto to keep water and mud off the buttons. mine has survived 4 years in a harsh river cave survey because of wrapping it in plastic. only the laser lense piece is exposed.

good luck and have fun.
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Re: Surveying large passage for the first time

Postby Jeff Bartlett » Sep 10, 2012 10:39 am

Yep, use a clipboard with big gridded paper; Rite-in-the-Rain #1110 is your best friend. You can get a cheap plastic clipboard at Wal-Mart to start out, or I've found thin and lightweight aluminum clipboards at office supply stores (NOT the huge ones that you can put, like, your lunch inside) that I haven't yet managed to break.

If you have access to a laser rangefinder, use it to correctly locate major features in the room and points along the walls, sketch those in very lightly, then work your way down the tape while drawing the passage. Chad's suggestion to leave the tape down is a good one.
"Although it pains me to say it, in this case Jeff is right. Plan accordingly." --Andy Armstrong
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Re: Surveying large passage for the first time

Postby Bob Thrun » Sep 10, 2012 11:56 am

In wide passages I often survey along both walls and take shots between the two sides. In some large rooms I have stations that are two shots from the nearest wall. This is why my computer program does not use left and right wall distances. I like to keep my shots in the 20 to 30 foot range for both ease of sketching and accuracy. I use a clipboard in larger passages. I like plastic drafting film for sketching. It requires special plastic pencil leads so the sketch is waterproof. I put a gridded sheet of white film underneath the translucent drafting film so I can sketch to scale with a protractor. I tie a small compass to my clipboard or sketchbook to keep it aligned with north.
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Re: Surveying large passage for the first time

Postby GroundquestMSA » Sep 10, 2012 1:55 pm

Bob Thrun wrote:In wide passages I often survey along both walls and take shots between the two sides.


I don't quite follow. Do you mean that you survey in a zig-zag from one side to the other, or that you survey each wall independently and shoot to the other side for passage width?

Bob Thrun wrote:In some large rooms I have stations that are two shots from the nearest wall.


Because you limit your shots to 20 or 30 feet, or for some other reason?

Bob Thrun wrote:This is why my computer program does not use left and right wall distances.


Because you are shooting azimuths wall to wall? How do you determine the cave length in that case?
Forgive me if I'm grossly misunderstanding, I'm pretty new to the language of survey. "Computer program," for instance, is an as yet unexplored aspect of my cartography.
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Re: Surveying large passage for the first time

Postby Martin Sluka » Sep 10, 2012 2:47 pm

Bob Thrun wrote:In wide passages I often survey along both walls and take shots between the two sides. In some large rooms I have stations that are two shots from the nearest wall. This is why my computer program does not use left and right wall distances.


Many problems solve DistoX + PocketTopo or other program for online sketching or DistoX + Auriga. You may change the scale, use splayshots, etc.
Survex (or Therion inspired by Survex) has quite powerful possibilities to work with such complicated data: flags ignore, duplicate, nosurvey, ... Check Survex manual: http://survex.com/docs/manual.pdf
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Re: Surveying large passage for the first time

Postby GroundquestMSA » Sep 10, 2012 3:05 pm

Martin Sluka wrote:Many problems solve DistoX + PocketTopo or other program for online sketching or DistoX + Auriga. You may change the scale, use splayshots, etc.
Survex (or Therion inspired by Survex) has quite powerful possibilities to work with such complicated data: flags ignore, duplicate, nosurvey, ... Check Survex manual: http://survex.com/docs/manual.pdf


Thanks Martin, I know, use Therion or Survex and all my wildest dreams will come true. Unless you were trying to help Bob, who seems to have everything under control...
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Re: Surveying large passage for the first time

Postby Chads93GT » Sep 10, 2012 4:00 pm

GroundquestMSA wrote:
Martin Sluka wrote:Many problems solve DistoX + PocketTopo or other program for online sketching or DistoX + Auriga. You may change the scale, use splayshots, etc.
Survex (or Therion inspired by Survex) has quite powerful possibilities to work with such complicated data: flags ignore, duplicate, nosurvey, ... Check Survex manual: http://survex.com/docs/manual.pdf


Thanks Martin, I know, use Therion or Survex and all my wildest dreams will come true. Unless you were trying to help Bob, who seems to have everything under control...


Lol. Good one.


Anyway. Big passage surveys sometimes survey along both walls and shoot connection shots between for more accuracy in sketching. LRUD has nothing to do with cave length only passage volume. Sometimes LRUD is too far away so it's left out. Profiles can be used to show how big the passage is anyway so a LRUD at each station isn't really necessary. That being said I always take LRUD measurements.
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Re: Surveying large passage for the first time

Postby Extremeophile » Sep 11, 2012 10:49 am

We've been using flexible clipboards with 8.5x11 paper for big passage sketching here in the West. These pack better and don't easily break. Almost all the surveying I do anymore uses a Disto for distance. We've been taking 2 Distos; one for the survey distance measurement, and another for the sketcher for accuracy of passage details. I'm familiar with the arguments for using a tape and leaving it in place, and limiting the length of survey shots, but with Distos it's possible to eliminate the need for survey tapes and short shots without sacrificing accuracy.


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No, I'm not happy to see you... that is a Disto in my pocket.


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Some big passage sketching on large paper.


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More big passage sketching.


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It's hard to fit big passage on 5x7 paper, even at 50'=1" (600:1)


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Big passage sketch in Mammoth Cave.
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Re: Surveying large passage for the first time

Postby George Dasher » Sep 11, 2012 11:32 am

Just take your time, and take splay shots where you need to.

A clipboard and a Disto may also help.

Also don't skip the wall dimensions because the walls are too far away--that's a good time for a splay shot, if they are that far away.

I hope it is a nice stream passage without too many formations, breakdown, and/or side leads. Those can be in incredibly fun to survey. Or a long sand-floored passage.
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Re: Surveying large passage for the first time

Postby Martin Sluka » Sep 11, 2012 12:00 pm

Extremeophile wrote:We've been using flexible clipboards with 8.5x11 paper for big passage sketching here in the West.


Just to remind you: http://cachtice.speleo.sk/impregnation/index_en.html
There is a guide for self made sheets with millimetric paper on one side and surveying table on another waterproofed by polystyrene. Tested many times. One may sketch huge passages on two or more sheets together (not hanging in pit).

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Last edited by Martin Sluka on Sep 13, 2012 3:44 am, edited 1 time in total.
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Re: Surveying large passage for the first time

Postby lleblanc » Sep 11, 2012 2:17 pm

Martin Sluka wrote:Many problems solve DistoX + PocketTopo or other program for online sketching or DistoX + Auriga. You may change the scale, use splayshots, etc.Survex (or Therion inspired by Survex) has quite powerful possibilities to work with such complicated data: flags ignore, duplicate, nosurvey, ... Check Survex manual: http://survex.com/docs/manual.pdf


I concur with Martin. I may sound like I'm preaching for my own church, but given the software is free, I feel less shame ;)

Using a PDA, you may take a lot of splay measures to walls, rocks, stalactites or any other significant detail that can help you sketch. These will automatically appear on your line plot, making your sketch like drawing by numbers. You may indeed do the same on paper, but you may find it tedious to draw all those lines manually before you start sketching.

Few PC software support splay measures. Compass will eventually, and Therion already does. But since sketching takes place underground, it's not so important when you're back home. The upcoming (September) version 2.05 of Auriga will export survey shots as a CSV file, with splay measures as an option. A tester tells me he got good success at importing this file into Therion, including splay measures.

Leaving the measuring tape on the ground may help sketching a bit, but at best you have only one tape, and none if you use a laser rangefinder. And laser beams don't tend to persist for long once the Disto is turned off or moved ;)
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Re: Surveying large passage for the first time

Postby GroundquestMSA » Sep 11, 2012 7:26 pm

George Dasher wrote:I hope it is a nice stream passage without too many formations, breakdown, and/or side leads. Those can be in incredibly fun to survey. Or a long sand-floored passage.


It's a strange, upper level, decorated, flowstone and breakdown floored passage. There are two massive mounds of what I assume is old breakdown covered in flowstone. There are a few holes in the floor with gnarly breakdown maze. There is a great big pothole. It's altogether more complex than anything I'm used to, and I'm exited to give it a try.

Thanks for the tips so far.
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Re: Surveying large passage for the first time

Postby Jeff Bartlett » Sep 12, 2012 3:53 pm

lleblanc wrote:Few PC software support splay measures. Compass will eventually, and Therion already does.


Alright Luc, you lost me on this one. Huh?
Do you mean they don't support splay exports from Auriga, or that they don't support splay shots in general (without Auriga)?
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Re: Surveying large passage for the first time

Postby lleblanc » Sep 12, 2012 6:07 pm

Jeff Bartlett wrote:
lleblanc wrote:Few PC software support splay measures. Compass will eventually, and Therion already does.


Alright Luc, you lost me on this one. Huh?
Do you mean they don't support splay exports from Auriga, or that they don't support splay shots in general (without Auriga)?


Most PC survey software don't know about splay measures at all. They just handle plain survey shots between stations, not between a station and some arbitrary (non-station) detail. Correct me if I'm wrong, but I get occasional requests to port Auriga to the PC precisely to support such features. I don't want to go that way because, conversely, PC programs do a lot of things Auriga doesn't do (and doesn't have to, being oriented to in-cave use). Instead I suggest users to ask for such simple features to the author of their favorite PC program. Larry Fish told me splay measures are in his plans for Compass, and I know Therion already recognizes them. Any other?

While I'm at it: in Auriga, if you add survey shots (not splay measures) to help with sketching a large passage, it's easy to exclude them from cave statistics to avoid exaggerating development (just set their "Exclude from Statistics" attribute). Of course splay measures never count in statistics.
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