Offset cross-section view lines

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Offset cross-section view lines

Postby trogman » Jun 17, 2013 6:59 am

Maybe someone can give me some advice on this question: I want to depict a section view of an entrance pit, but about 12' down the pit is offset about 5,' and I wanted to do a 90 degree turn in my section line, and then another 90 degree turn, and then across a large room. In cases such as this would it be OK to show the section line where it passes through the cave? I know with a standard straight-line section, the line would not normally be shown. However, in this case, there would be no other way for the map reader to interpret where the section lines turn.
It is done that way in mechanical drawings all the time, which is what I am more familiar with. However, conventions in cave cartography are somewhat different.

Looking forward to your suggestions.

Trogman :helmet:
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Re: Offset cross-section view lines

Postby Chads93GT » Jun 17, 2013 2:07 pm

you are wanting to draw a running profile of the cave? This generally follows the survey line, regardless of how sharp the turns are, Adding a zig zag line through the map may clutter the map up. do what works. This is just what has been suggested/explained to me in this region.
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Re: Offset cross-section view lines

Postby GroundquestMSA » Jun 17, 2013 2:09 pm

In this case aren't you (like Chad says) really drawing a selected section of profile? Either way, I suppose the only thing that matters is that the map is understandable. If I understand your situation properly, you're looking to do something like the top example below? How about the bottom example, does that make sense too?

click to enlarge
Image
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Re: Offset cross-section view lines

Postby Extremeophile » Jun 17, 2013 3:08 pm

I believe what you are describing would best be described as an idealized profile view.

See http://www.forums.caves.org/viewtopic.php?f=26&t=7940

Basically you mix the projection angles a bit to give a profile that better represents the experience you might actually get while traveling through the cave. It's a more subjective cartography technique, but may result in a more useful map. I don't think you necessarily need to draw a projection line through the cave passage to show each change in angle, but you should label the profile view as "idealized".

Dwight Livingston is sometimes on CaveChat. His excellent award winning Shoveleater map has many profiles where the projection angle changes. He does a good job of representing these angle changes.
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Re: Offset cross-section view lines

Postby trogman » Jun 17, 2013 6:35 pm

Here is a very simplified version of what I am thinking of:


Image

The pit entrance is slightly offset, and there are some features and passages in the lower parts of the cave that I would like to portray in the same section view as the entrance pit.
This map will have at least 7 section views, which I am putting on a second sheet. I suppose I could use an idealized profile for A-A, and that way I could do w/o that line running through the middle of the room.
Just to clarify, the map I have posted here is not the map I am working on.

Thanks for all the suggestions!

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