Sketching from memory instead of surveying.

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Re: Sketching from memory instead of surveying.

Postby driggs » Mar 13, 2013 6:50 pm

Chads93GT wrote:You sure do assume a lot about me David.


Nothing personal, I don't really know a thing about you. My point is that when you produce a survey and/or map, it is useless for some very legitimate scientific purposes* if the quality is unknown.

Now, as to whether it truly speaks to the quality of the survey just because somebody scrawled "BCRA Grade 5" across their map, who knows. If it says "Grade 5", at least I know that the survey team thought they were doing a top-notch modern survey rather than simply running through the cave counting paces.

And, that said, I know of some pretty amazing mappers in Missouri, and I've a hard time believing "we don't grade maps in MO". Say it ain't so, Spike! :yikes:

* All those examples are real life uses of cave survey data and maps that I'm personally aware of in WV... though we cheated and tied in to a radio location for the farmer's well site.
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Re: Sketching from memory instead of surveying.

Postby Chads93GT » Mar 13, 2013 11:32 pm

It's ok David. I really do get wha you're saying. It's just In Missouri, maps aren't graded. I've never seen a mo map with a grade but I've seen plenty of tag maps with grades. I assume its a regional thing. I'm still relatively new as I've only been mapping caves for 4 years and 6 or 7 miles total. I would assume our maps/surveys are 5 grades as we laid our plot line on the topo map and opened up a new entrance to the cave and it was two miles in and withing a couple feet of the actual plot line on the surface. Be that as it may. We just don't write grade 4 or 5 on the map. Generally we shoot for 2* of error but I prefer 1*.

If spike is putting grades on maps I've yet to see them. He must be hiding them in his stash lol.
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Re: Sketching from memory instead of surveying.

Postby Bob Thrun » Mar 14, 2013 2:45 am

The term Sketch From Memory is more understandable than Grade Something-or-Other. It does not require a separate explanation. When I started caving, I saw some maps with a survey grade and did not know what it was. When I learned that the grade indicated how the survey was done, I was disappointed. That could have been stated on the map in Plain English. Survey Grades have been a peeve of mine ever since. I argued to abolish grading at the meeting of the Survey Grades at the International Congress of Speleology in 2009.

There have been several slightly different definitions of Survey Grades: CRG 1950, CRG 1966, BCRA 1976, BCRA 2002, ASF, and UIS. If you give a grade, you should also state which definition. CRG 1966 and BCRA 1976 were defined in terms of accuracy. The specifications were given as plus-or-minus tolerances. I interpreted this to mean a uniform distribution as I would for a machined part, not a standard deviation. Nobody ever tried to show that their surveys actually met the accuracy standards. Instead they called every compass, tape, and clinometer survey Grade 5. The BCRA 2002 revisions made the specifications more closely match reality. In the furor after the change, I published an article with my thoughts about Specifying Survey Quality in Compass Points 31 http://www.chaos.org.uk/survex/cp/CP31/CP31.pdf .

I looked at closure errors from over 40 caves and gave a talk at the 2000 NSS Convention. I did not find any Grade 5 surveys and there were some near Grade 3.

Missouri has long had a tradition of excellent cave maps. Some of the early cave mappers were very good and later mappers matched their quality. Lang Brod once said there is no point in assigning a grade number if all the maps are the same grade (Missouri Speleology, Vol. IV, Nos. 1-2, p. 48).

Regarding significant digits: I started surveying writing station-to-floor and station-to-ceiling distances in my notes. I changed to station-to-floor and total passage height when I found I had some 53-foot high passages. No significant accuracy is gained by recording distances to the centimeter or inch/tenth foot. The larger angle errors determine the survey accuracy. The optimum length unit would be about 10 cm. However, I record the smaller units because they are numbered on the tape.
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Re: Sketching from memory instead of surveying.

Postby batrotter » Mar 14, 2013 5:06 am

I would like to commend you for taking the effort of doing a map. It doesn't matter if it's not up to someone elses standards. A sketch map for a small cave is a 1000% better than no map. At least you are providing some sort of info to the caving community. Unfortunately, in Indiana, we have plenty of people that want information such as cave locations, but they won't take 5 minutes to fill out a report form on something new.
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Re: Sketching from memory instead of surveying.

Postby trogman » Mar 14, 2013 6:53 am

With regards to assigning grades, I have in the past stated that my maps were "Grade 5 Survey." I confess at the time I did not understand the definition of "Grade 5," and thought it simply meant I had used a tape, compass, and clino. A map a entered in the SERA Map Salon recently was penalized for not having any reference to either the type of instruments used or the survey grade. The problem I run into is that oftentimes I will use a variety of instruments, and to list them all would be a bit overkill, in my opinion. "Survey conducted using tape, compass, clinometer, laser distance measuring tool, laser clinometer, etc., etc." You get the idea. I suppose "clinometer" could be defined as any type of angle measuring device, and the term "disto" could be applied to any laser measuring tool. (Although "disto" is actually a brand name, and I use a Bosch) Nonetheless, listing every measuring tool can get a bit tedious; it would be useful to have a short tagline that describes how accurate the survey is, without all the complexity of the various BCRA grades.

To return to the original topic, I think in some instances a sketch map is far better than no map at all. By the way, Groundquest, your "sketch from memory map" is pretty dang good! I have seen (and drawn) some tape and compass survey maps that didn't look nearly as good.

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Re: Sketching from memory instead of surveying.

Postby Extremeophile » Mar 14, 2013 8:10 am

trogman wrote:By the way, Groundquest, your "sketch from memory map" is pretty dang good!

How would you know that without having been to the cave :shrug:
I've seen a number of beautiful and detailed sketches that in no way represent reality. Some maps belong in the fine arts salon rather than the cartography salon. I think the larger point David was bringing up is understanding the difference between precision and accuracy. By stating a length and depth, sketching fine details, etc. you might represent what most would interpret as a high level of precision, but without survey data (accuracy) then it's just art.
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Re: Sketching from memory instead of surveying.

Postby Scott McCrea » Mar 14, 2013 8:39 am

It depends on the situation. This one was well served by a sketch map. Some times you have to settle for "good enough" and move on.

"Insanity is often the logic of an accurate mind overtasked."
Oliver Wendell Holmes
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Re: Sketching from memory instead of surveying.

Postby trogman » Mar 14, 2013 9:12 am

Extremeophile wrote:
trogman wrote:By the way, Groundquest, your "sketch from memory map" is pretty dang good!

How would you know that without having been to the cave :shrug:


No doubt. This is true whether the map is a "sketch from memory" or a based on survey data. I was just complimenting the quality of his drafting; I have no way to know how accurate it is.

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Re: Sketching from memory instead of surveying.

Postby MUD » Mar 14, 2013 9:55 am

:big grin: Y'all go survey while I scoop more virgin lol! :laughing:
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Re: Sketching from memory instead of surveying.

Postby Spike » Mar 14, 2013 10:16 am

First I'd like to chime in concerning sketch maps, versus survey. They are what they are, they give an idea of what is there are are just as useful as sketch on a dry erase board, which I have drawn to explain to someone what a cave "does." Once again, they are what they are. Any justification on why they are a sufficiant replacement for the typical surveyed map is pretty much hogwash IMHO. Maps of small caves are quite useful and I use them a lot to do in the field doing bio work and for figureing out duplicate reports of the same cave.

Concerning survey grades and the Show Me State.

I survey to Grade 5 with the caveat that we are reading to tenths or half tenths on the tape, which is not quite to the cm, but that differnce is silly in the scheme of things. About half of the other "good" mappers I know actually do a Grade 4 (and I'll give it a + for effort) for either not calibrating the compass(I consider using a geomag calculation a calibration, if a poor one), and read +/- 2 degrees. Such is life.

Do we scrawl BCRA Grade Rockstar on the map, nope. Do I think it mattters, nope. Should we, yeah, cause there is a world of difference between the upper grades and the lower grades. But having some experience with the doing the things Riggs mentioned. I don't just want the map for that, no matter the number of cross-sections, profiles, location of 0 datum(my favorite joke to see on a map). I want your data, I want every survey shot and I want it digital. If I'm going to spend the money it would take to drill a shaft into a remote section of the cave, I want the numbers, and I want to see your blunders that hide behind the grade. That being said, if your data isn't good enough to do those things Riggs mentioned. Collect better data.

My 3 cents.
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Re: Sketching from memory instead of surveying.

Postby UnderGroundEarth » Mar 14, 2013 10:58 am

trogman wrote: A map a entered in the SERA Map Salon recently was penalized for not having any reference to either the type of instruments used or the survey grade.



Stephen, The SERA Salon is starting to judge maps based on the same standards set for NSS Cartographic Salons. This is probably why you were penalized a few points for not having the grade or the insturments used on the map.

For NSS judging criteria go to - http://caves.org/committee/salons/Carto ... udging.htm

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Re: Sketching from memory instead of surveying.

Postby Jeff Bartlett » Mar 14, 2013 11:46 am

Extremeophile wrote:
trogman wrote:By the way, Groundquest, your "sketch from memory map" is pretty dang good!

How would you know that without having been to the cave :shrug:


Exactly the problem with the cartography salons, actually! By definition, they can't actually judge the cartography.
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Re: Sketching from memory instead of surveying.

Postby Jeff Bartlett » Mar 14, 2013 2:51 pm

Chads93GT wrote:I've never seen a mo map with a grade but I've seen plenty of tag maps with grades.

It's a standard for TCS, not sure about ACS or GSS. I never put "grade 5" on my maps before moving here, either.
And it's bogus for the following reason.

Most TAG mappers: Compass/Clino read to whole numbers, no backsights, no maximum loop closure error, tape read to tenths, no instrument calibration (BCRA Grade 5)
Me: Compass/clino read to 0.5, backsights within +/- 2.0, systemwide loop UVE (Walls) <2.00, tape read to tenths, no instrument calibration (BCRA Grade 5)
CRF/Spike: Compas/clino read to 0.5, backsights within +/- 1.0, likely tighter loop closure rules, tape read to half-tenths, calibrated instruments (BRCA Grade 5)
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Re: Sketching from memory instead of surveying.

Postby Chads93GT » Mar 14, 2013 3:12 pm

Jeff Bartlett wrote:
Chads93GT wrote:I've never seen a mo map with a grade but I've seen plenty of tag maps with grades.

It's a standard for TCS, not sure about ACS or GSS. I never put "grade 5" on my maps before moving here, either.
And it's bogus for the following reason.

Most TAG mappers: Compass/Clino read to whole numbers, no backsights, no maximum loop closure error, tape read to tenths, no instrument calibration (BCRA Grade 5)
Me: Compass/clino read to 0.5, backsights within +/- 2.0, systemwide loop UVE (Walls) <2.00, tape read to tenths, no instrument calibration (BCRA Grade 5)
CRF/Spike: Compas/clino read to 0.5, backsights within +/- 1.0, likely tighter loop closure rules, tape read to half-tenths, calibrated instruments (BRCA Grade 5)


I do what CRF/Spike: does.
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Re: Sketching from memory instead of surveying.

Postby GroundquestMSA » Mar 14, 2013 3:54 pm

Extremeophile wrote:
trogman wrote:By the way, Groundquest, your "sketch from memory map" is pretty dang good!

How would you know that without having been to the cave :shrug:
I've seen a number of beautiful and detailed sketches that in no way represent reality. Some maps belong in the fine arts salon rather than the cartography salon. I think the larger point David was bringing up is understanding the difference between precision and accuracy. By stating a length and depth, sketching fine details, etc. you might represent what most would interpret as a high level of precision, but without survey data (accuracy) then it's just art.



So does this suit you better? Is the lack of detail and distance estimates enough to impress upon the viewer that this was not a precise survey? Why my attempt at capturing the essence of the cave by including the details as I remembered them should be counted against me is truly baffling. What part of "very approximate sketch from memory" is going to make people think the inclusion of rocks and dirt and slopes is a claim of accuracy?
Image

Spike wrote:They are what they are, they give an idea of what is there are are just as useful as sketch on a dry erase board, which I have drawn to explain to someone what a cave "does."


They are indeed what they are. They tell what a cave "does," and can also tell how it does it. That's all that many people want a map for. A sketch map can tell you the nature of the cave passages, not only their estimated orientation. They can tell you if the cave is worth a visit for photos or digging or if there is a stream or a pit or a dinner buffet. My point is that a cave map doesn't have to be a precise, scientific, or even very accurate document in order to be extremely useful.
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