Cartography question

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Cartography question

Postby KeyserSoze » Sep 16, 2009 2:31 am

So I've started drafting my first cave map with illustrator. I think I've been doing a good job so far, but I'm not sure how to correctly represent some of these confusing parts. The problem with mapping this cave is that the passage repeatedly opens up small floor canyons that you must climb down into to reach the lower level where the passage opens up. After these climb downs, the upper passage continues only a short distance before becoming too low or narrow for travel. This trend is repeated several times and appears that it will continue to do so.

So to summarize, I need to make a plan view for a multi-level cave where each lower-level passage lies directly underneath the upper passage. This is creating an abundance of passage overlapping in the plan view that is very hard to represent in a way that is easy to understand. If the continuing upper passage was anything significant I would of course survey it and display it on a separate plan view, but the sections are so short (less than 30 feet) that it really seems unnecessary to do so.

What I've currently done is to switch the cave walls to the overlying passage symbol right at the spot where the climbdown and survey drops are located, and then to show the cave details for the lower level from that point on. On the plan view I displayed the overlying passage as unsurveyed. Is this an acceptable solution or should I be doing it a different way? Would it be acceptable if I just ignored the passage overlapping on the plan view all together as long as the climbdown and drop distance is noted?




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And btw the profile view looks wierd because I enlarged it from half scale in order to make this image.
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Re: Cartography question

Postby Anonymous_Coward » Sep 16, 2009 8:48 am

Keyser,

I can't see the image but I would suggest that you survey ALL the passages no matter how insignificant you think they are and no matter how much of a pain in the ass it is to survey them. Your map will be much better off if you do. You may not need a separate plan view for the upper level, but it needs to be portrayed accurately. (Survey it)

Your plan may look a little confusing with the two levels, but if you have a nice projected profile it should help to clear things up. Cross-sections that show the relationship would help as well. If the upper level segments are insignificant, I would limit floor detail to the lower level and show the upper one as a ghost above it.

Try to re-post the map so we can see what you are talking about.
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Re: Cartography question

Postby KeyserSoze » Sep 16, 2009 2:46 pm

Thanks for the input, and for the reminder to include more cross sections. I did consider surveying the short continuing sections of the upper passages (which would only be 1 shot in most cases, and would be impossible to back-shot btw), but when I really put some thought into it I realized that it's just not going to make the map any more clear. The issue I'm having is not with survey data for the upper passage, it's simply cartography. I don't know how to represent the transition from upper to lower passage in a situation like this. One idea I had was to leave the map basically like it is, but to draw a strait line through the passage right at the transition, and then label the line with a note for clarification. Would something like that be acceptable to do?

Here is the raw link. This should work.
http://img37.imagevenue.com/img.php?ima ... _595lo.jpg
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Re: Cartography question

Postby Anonymous_Coward » Sep 16, 2009 5:35 pm

Still can't see it. I get a "cannot display" message. Might be a problem on my end. Sorry.
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Re: Cartography question

Postby Bob Thrun » Sep 16, 2009 7:20 pm

When I tried to view your picture, I got a message telling me to consent to Imageveneue rules. I do not know about Imagevenue or its rules. I am not about to do what amounts to signing a blank check. I suggest you post your picture in a way that can be simply viewed without complications. I have posted pictures here that can be viewed without Imagevenue. You should be able to do the same.
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Re: Cartography question

Postby Scott McCrea » Sep 16, 2009 7:48 pm

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Re: Cartography question

Postby KeyserSoze » Sep 16, 2009 11:53 pm

This one should work, imageshack always works. Let me know what you think.


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http://img44.imageshack.us/img44/5782/examplesurveysection.jpg/
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Re: Cartography question

Postby rchrds » Sep 17, 2009 9:14 am

Okay- this is always difficult, and as an earlier poster mention, the key to really describing the passage will be cross-sections- numerous cross-sections. Of course, the standard is a cross section in the sketches at every station, but everyone knows that doesn't often happen. For the carto side, I think what is important is which layer has more floor/ceiling details that will need to be depicted. It is difficult to tell, in your drawing, for example, if the stalagtites and sodastraws (which should always have a page downward or upward orientation, BTW) are in the upper or lower level. I am going to assume that they are in the upper level. The brown dirt/cobble detail, I am going to guess is in the lower level, but being in a strip like that is very strange with no other floor detail to show the rest of the floor makeup. I think that you could do a couple of things.

The outer wall, regardless of underlaying passage, should always be solid (unless it is unsurveyed, but you indicated that you surveyed the lower level, so there should be a solid wall. The solid wall absolutely takes precedence over an unsurveyed one.) Your left wall changes from solid to dashed, I assume to show that there is an underlaying passage. But there is no indication as to why it changed, no beginning of the lower or upper passage, so why it changed is unclear. Same with the short section of right wall. The center wall being dashed is alright, but again, there is no indication as to why it suddenly started.

The dirt. I cant tell you how confusing the dirt floor detail is. It makes no sense to me at all. If you are going to show floor detail, you need to show consistent detail across the passage width.

Once you have decided which layer to show details for (upper or lower) show all the details, and then notate that upper layer floor details have been omitted for clarity, and show only the walls.

Hope this is a start.

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Re: Cartography question - think out of the "box"

Postby Pat Kambesis » Sep 17, 2009 5:33 pm

Displaying complex multi-level canyon passage, in a clear and concise manner is a challenge. You could map every nook and cranny but rendering it cartographically in plan view so that is clear and useful is almost impossible unless you use multiple pull out sections - but even these may eventually also clutter up the map so its even harder to read.

One thing that should be remembered about ANY type of cartography is that a map is a generalization of the real world. It is impossible to include every smidgeon of detail on a map. On mode that I've thought of using is to actually use a passage wall symbol that denotes "complex, multilevel canyon passage" - for this I added filled in hatures that faced inward, directly on each wall. This passage symbology is then accompanied by cross sections at every station and or anywhere that the passage undergoes a significant change in shape or includes some notable feature or obstacle.

A profile will also be useful to indicate whats going on at ceiling and floor level with symbology or notation to indicate important wall features (this is challenging but can be done).

However you decide to address, the bottom line is that it should enhance the readability and usefullness of the map. If a map is difficult to read or obscure and confusing in its rendition, then it is useless.


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Re: Cartography question

Postby Dwight Livingston » Sep 17, 2009 8:09 pm

Keyser

I'm interested in the answers here, especially with Pat in the conversation. I've attached an example of an over/under segment of a map I'm doing. I'm not saying do it like this, just sharing a bit of map that I've been struggling over. I'm not sure I have it as I want yet. And as everyone else is saying, I will be including sections and a profile, so someone can figure it out with a little work. Still, I'd like the plan to read as clearly as I can.

A comment on your example. I believe the stalagmite, stalactite, and column symbols should be shown upright to the page and not tilted to the passage.

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Re: Cartography question

Postby Pat Kambesis » Sep 17, 2009 8:55 pm

Dwight is correct - the speleothem symbols should not have an angled orientation i.e. they should be straight up and down i.e. parallel with the main axis of the top of the page. On the symbols themselves, though I don't have a good solution at the moment, we need a speleothem symbol that doesn't need to oriented with "up" being the top of the map/page (what if we want to turn the map upside down or sideways?)

Dwight, your map segment is very nicely done. Its very obvious that there is a lower level passage that is accessed by pits in the floor. A suggestion to make it even more clear is to use shading to show the lower level rather than a dashed line- usually some light shade of grey works best.

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Re: Cartography question

Postby Jeff Bartlett » Sep 18, 2009 8:52 pm

Seconded on Dwight's map. Good stuff. I have two points to add:

1. Composite cross-sections are your best friend in this instance. Canyons are funny like that, they always seem better-represented in cross-section than the other views. The reason composites excel in these situations is they not only show you the shape of each passage but the relationship from one to another. If the passages on different levels have different names, this is also a great place to label which is which.

2. When you have overlapping passages with essentially the same passage trend (one a paleo-version of the other, or separate enlargements in the same joint), I think oftentimes the "overlying passage" and "underlying passage" symbols can start to be more confusing than helpful. This is especially the case when there are more than two levels. It's probably easier for the map viewer if you simply draw the uppermost level, allowing the lower levels to poke out where applicable, and make use of offsets to show the plan view of the lower level(s). PK put it best, all cartography is a compromise between the reality and the paper and your primary goal should be for the map to be understood by the viewer with as little "translation" as possible. I don't think the dotted-line wall symbols are particularly intuitive, and when the passages are parallel to each other you can do more harm than good in terms of map usefulness.
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Re: Cartography question

Postby Bob Thrun » Sep 19, 2009 3:57 pm

Pat Kambesis wrote: On the symbols themselves, though I don't have a good solution at the moment, we need a speleothem symbol that doesn't need to oriented with "up" being the top of the map/page (what if we want to turn the map upside down or sideways?)

The suggestion that the symbols should be such that the map could be rotated to any orientation was made many years ago by a British caver on the old Cavers Digest. The problem is that we expect soda straws and stalactites to point down and stalagmites to point up. We also have the convention of text being horizontal.

With present computers we could set up a font of stal characters that would remain vertical when the map is rotated. We could have different proportions for short thick stalagmites (boldface) and for long thin stalactites. The symbols could be centered a point. We could change the point size for the size of the stal when the stals are large enough to be shown individually. I suspect there would be problems with some of the symbols bumping into reach other as a block of them is rotated.
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Re: Cartography question

Postby Stan Allison » Sep 20, 2009 12:19 pm

On the symbols themselves, though I don't have a good solution at the moment, we need a speleothem symbol that doesn't need to oriented with "up" being the top of the map/page (what if we want to turn the map upside down or sideways?)


Actually there is a good solution to the problem of speleothem and other symbols needing to maintain their "up" orientation even if the map is rotated. If you use Walls/Illustrator SVG roundtripping to draft your maps and place all of your speleothem and other "up" dependent symbols in the w2d_Detail_sym layer, then it will be possible for you to rotate your map even to something as strange as 134.3 degrees and still have the speleothems maintain their "up" orientation. I was recently drafting a cave map as we explored a cave using Walls/Illustrator. Since I didn't know the extent of the cave, I started drafting the map with the standard North being up. As we explored and surveyed the cave, I realized that the ideal orientation for the map would have north on the right side of the page. I was easily able to roundtrip the map in Walls and rotate it 90 degrees and have all of the speleothem symbols, ceiling heights, pit depths and mud/clay symbols maintain their proper ''up" orientation. This saved me a lot of work. OK, Martin Sluka, it has been a while since we've heard from you. This is your opportunity to mention that Therion can do the same! :big grin:

Sorry to get a bit off topic.

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Re: Cartography question

Postby Spike » Sep 21, 2009 10:26 am

While talking about Stal symbols and rotation, how many sketchers rotate the book while sketching? I know I have done it and I know others do it. I see upside down text on notes pretty often. And it makes me wonder if a Stal symbol is pointing up or down. I recommend making a conscious effort to place all text and Stal symbols with the same orientation. Also I am a firm believer in placing North at the top of every map. It's a standard cartographic principle, and one I would only violate if I was adapting a map for a wayside or other type of visitor display that may have layout constraints.

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