Slope Calcs

[Monkey]

I have come across a problem in my survey book, if anybody has any suggestions that would be big help.

Cross Section Notes: LT 8.6/24.9, 8.4/21, 6.2/0(CL), 5.8/10.5, 4.2/18.3 RT

What is the average slope across this Cross-Section.

I come up with two ways? Which one seems appropriate or is there any other method?

Average=10.46% and By Linear Regression-9.62%

slope.xls

 

[ptatohed]

I have come across a problem in my survey book, if anybody has any suggestions that would be big help.

Cross Section Notes: LT 8.6/24.9, 8.4/21, 6.2/0(CL), 5.8/10.5, 4.2/18.3 RT

What is the average slope across this Cross-Section.

I come up with two ways? Which one seems appropriate or is there any other method?

Average=10.46% and By Linear Regression-9.62%

Monk, I think you might be making this too complicated. And I'd recommend that you do not rely on Excel. With that said, maybe I am making this too simple? But I get (8.6 - 4.2) / (24.9 + 18.3) = 10.2%

Are there 4 multiple choice answers?

 

[Monkey]

No, there are no answers in the book, that was just an example of notes from an Old Surveying Text. But, what do you do when you have both as your choices, 10.2 and 10.46.

The key word here is "average".

 

[bradlelf]

10.18 is correct; the key word in the question is average. It seems like you are over thinking this. Left most station to right most station; delta y over delta x.

 

[Monkey]

So, that would be the option to go with, instead of taking an average of slopes at every point?

10.2 or 10.18 instead of 10.46, any other method would be losing time on the test. Reza Malhatti, (Instructor, http://www.surveyingreview.com/)for suggested taking a weighted average, that would be the best choice. And I do not know how would you do that with the set given.

Thanks

 

[ptatohed]

So, that would be the option to go with, instead of taking an average of slopes at every point?

10.2 or 10.18 instead of 10.46, any other method would be losing time on the test. Reza Malhatti, (Instructor, http://www.surveyingreview.com/)for suggested taking a weighted average, that would be the best choice. And I do not know how would you do that with the set given.

Thanks

I actually played around with a weighted average yesterday but didn't bother mentioning it because I still got the same 10.2%. Here's what I did though:

(3.9/43.2)(.2/3.9) + (21/43.2)(2.2/21) + (10.5/43.2)(.4/10.5) + (7.8/43.2)(1.6/7.8)

But to me, when you are talking about grading, the average slope is catch point to catch point.

 

[Monkey]

Thanks that helps a lot.