Newb Map Question

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Newb Map Question

Postby Hatch » Jun 14, 2006 12:00 pm

What's the difference between Horizontal Length and Surveyed Length? I see both listed sometimes on the same map.
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Postby Squirrel Girl » Jun 14, 2006 12:07 pm

Imagine a big, vertical pit. The horizontal length may be about 25 feet, whereas the surveyed length may be 300 feet.
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Postby Hatch » Jun 14, 2006 12:11 pm

Ok, so if there's a 100 foot pit with 300 feet of passage at the bottom, then the Horizontal Length would be 300 feet and the Surveyed Length would be 400 feet?
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Postby Squirrel Girl » Jun 14, 2006 1:07 pm

Hatch wrote:Ok, so if there's a 100 foot pit with 300 feet of passage at the bottom, then the Horizontal Length would be 300 feet and the Surveyed Length would be 400 feet?
That's the way I'd look at it.
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Postby George Dasher » Jun 14, 2006 2:37 pm

Hatch:

You are correct: A cave with a 100 foot pit and 300 feet of passage at the bottom has a Horizontal Length of 300 feet and a Surveyed Length of 400 feet. If the pit is vertical and the horizontal passage is really horizontal, then the cave depth is 100 feet.

Surveyed Length can also be called Slope Length or Slope Distance, or Cave Length or Length. It is the length of the cave, and that is the term I prefer.

Horizontal Length is a map projection. I know there are people who are going to argue with this, but it counts for next to nothing. Slope Length is what you want to use.

By the way, I am capitalizing these terms for clarity. They are, in reality, common nouns.

Pits: A 100-foot pit on a 45-degree angle is still a 100-foot-deep pit. You use slope distance here too; this is so the next caver going down the thing has enough rope. The cave depth would be 50 feet or something like that.

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Postby Hatch » Jun 14, 2006 2:48 pm

I think I'll just get your book, George. :tonguecheek:
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Postby hewhocaves » Jun 14, 2006 3:58 pm

ka-CHING!
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Postby Squirrel Girl » Jun 14, 2006 4:08 pm

George Dasher wrote:The cave depth would be 50 feet or something like that.
71', I think.
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Postby Hatch » Jun 14, 2006 4:29 pm

The Sin(45) * 100 = 70.71 feet

It would also be the horizontal length. Man, I'm dragging up some trig from a long time ago.
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Postby ian mckenzie » Jun 14, 2006 7:22 pm

George Dasher wrote: A 100-foot pit on a 45-degree angle is still a 100-foot-deep pit. You use slope distance here too; this is so the next caver going down the thing has enough rope.
I'd say it's a 100-foot pitch, but a 70-foot pit. Unless it overhangs at 45 degrees, in which case it is both a 70 foot pitch and a 70 foot pit... god I can't believe I'm even typing this.
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