We were up working on a septic design expansion for Big Rock Campground and the owner wants to calculate the volume of the Big Rock that the CG was named after.
The rock (a glacial erratic) is over 30 feet high and 20-30 feet in diameter but the footprint of the rock is much smaller than the diameter (a serious overhang!).
I set up the Nikon Total Station and peppered the rock with reflectorless shots from 3 separate stations. Now I'm scratching my head as to how to calc. volume. I have Carlson/Acad 2009 and have done volume calcs in the past but none slopes greater than 100%.
Any ideas?
i don't know the shape of it, break comps in two portions. maybe compute the top (half) and add to the bottom (half). might take care of the disparity of undercut contours. just a WAG. enjoy the trip
Turn the rock over (rotate surface)?
DDSM:beer:
Sounds like a job for a Scanner.
B-)
I do not use Carlson, but Moe has the right idea. Pick an elevation that is near half way up from the ground and move all the points above that elevation to the side. Then you will have a pit/hole and pile/mound that you can calculate volumes from. Then add the two.
If you cannot get it to work or want to compare answers for the fun of it, email me a ASCII file (N,E,Elev,Desc).
Scott
Oh, I thought you were talking about my hometown for a second there.. Big Rock, Illinois!
scott
> I do not use Carlson, but Moe has the right idea. Pick an elevation that is near half way up from the ground and move all the points above that elevation to the side. Then you will have a pit/hole and pile/mound that you can calculate volumes from. Then add the two.
> If you cannot get it to work or want to compare answers for the fun of it, email me a ASCII file (N,E,Elev,Desc).
>
> Scott
It's a head-scratcher for sure. I wished I had a decent picture of the rock to show. ANother problem is that there is no clean way to slice the boulder in half at the fat part of the boulder is not necessarily a flat plane.
Rough AVERAGE measurements are 30' WIDE X 60' with probably an average height of 25 feet.
Hey Scott,
We enjoyed Traverse City and the rest of western MI last summer on vacation. Stayed at the State Park at the beach and rode bikes into town on the bike path for sandwiches and a beer.
THAT IS A TOUGH ONE
No matter how you slice it.....
Can you slice it vertically, and spin the 2 pieces to then create the surfaces?
How much do you suppose is below grade?
[sarcasm]Send the data to an engineer - they know how to do everything ...[/sarcasm]
scott
Is this it?
Must be some way to slice this thing into pieces you can work with.
Glad you enjoyed your time in Michigan. I am between Traverse City and Lake Michigan, nice area to work. Never enough time to relax. 🙂
scott
I don't understand why it can't be wireframe modelled and a volume computed from the model. Seems like it wouldn't be that big of a deal. If you want to share points with some of us, it sounds like a fun weekend challenge. The only caveat would be that the volume would only be the rock above the ground line. Can't calculate what you can't see.
As for laser scanning, I believe that is what has already been done - manually with the reflectorless. The accuracy of the volume/model is based on the number of shots.
THAT IS A TOUGH ONE
Here's a pic that shows part of the boulder. It's taken from the high side, so it's isn't nearly as impressive.:
scott
Don't worry about a 'flat plane'...parse the shots into three sets:
1: those shots depicting the 'fattest' (in plan view)make a surface called 'fat'
2: those shots 'under' the fat surface (using the fat points and the under points make a surface called 'under'.
3: those shots 'above' the fat surface (using the fat points and the above points make a surface called 'above'
Calculate the volume stratum using surface fat and above...and fat and under...add volumes.
DDSM thinking in C3D:beer:
DDSM
I like your thinking, :beer: :beer: :beer: :beer: to you.
If where you are is anything like here, you might want more :beer:
scott
> If you want to share points with some of us, it sounds like a fun weekend challenge.
I agree.
We are such nerdsB-)
Here's the ACII Points
The shots labeled "R" are random shots of the ground surface.
The shots labaled "ROK" are shots on the Rock Surface
The shots labeled S are stations.
This is just a quick and dirty calc for their website so I didn't waste too much time on it.
1,500.0000,500.0000,100.0000,S
10,497.8959,518.4471,100.9357,R
11,507.7333,530.9398,101.3184,R
12,499.8670,542.5918,104.1448,R
13,498.6043,552.7415,104.9573,R
14,526.6658,529.4733,100.6503,R
15,508.4289,531.4900,101.7217,R
16,530.6838,512.0791,101.4791,R
17,506.3492,532.9934,102.9397,ROK
18,500.5980,541.8976,106.2021,ROK
19,495.8015,547.6219,111.7146,ROK
20,509.1092,529.6963,107.9012,ROK
21,521.5941,527.6146,108.1594,ROK
22,531.3914,529.8878,107.8570,ROK
23,528.7739,527.2630,115.6035,ROK
24,523.8509,522.9371,116.7360,ROK
25,515.1202,523.1336,117.2449,ROK
26,509.4423,534.3827,128.7894,ROK
27,512.9313,526.0272,124.3290,ROK
28,519.7301,524.9116,120.7936,ROK
29,501.6915,539.7222,121.4540,ROK
30,514.7541,522.9942,117.6029,ROK
31,533.6105,531.9857,112.7168,ROK
2,490.6549,566.5944,105.5736,S
3,557.5518,525.2844,105.4565,S
44,509.5082,529.7956,100.6664,R
45,528.1044,557.4917,102.4963,R
46,530.3074,550.9398,128.1789,ROK
47,528.0777,558.7179,124.7739,ROK
48,523.7901,564.0776,119.6310,ROK
49,533.4687,548.2463,123.6636,ROK
50,516.2057,540.0075,129.9525,ROK
51,512.0582,531.7285,127.7622,ROK
52,521.2767,549.0204,131.1752,ROK
53,499.0908,555.1132,112.4196,ROK
54,530.0854,573.2398,107.6095,R
55,501.0017,548.5338,104.9268,R
56,500.7288,548.8300,107.1220,ROK
57,513.2475,562.0460,109.8160,ROK
58,504.2150,554.1705,120.5524,ROK
59,506.2332,551.6939,125.8288,ROK
60,503.0654,544.9911,127.1188,ROK
61,509.6138,552.6703,127.1014,ROK
62,501.5067,558.4236,113.3761,ROK
63,513.5798,562.6012,115.9861,ROK
64,517.9368,564.1441,104.3786,R
65,502.1379,551.9849,104.7141,R
66,498.1471,548.3586,118.5802,ROK
67,505.1549,557.1873,118.8453,ROK
I think I have an easy way
I'm drawing 2 foot contours (polylines) over the 30 feet of vertical of the rock.
I'll just ask autocad for the area of each polyline and multiply by 2 to calculate the volume of rock for each horizontal slice and add them up.
Here's the ACII Points
Approx 22000 units. In whatever unit system you're using.
Here's pretty pictures
I get 880 cu. yards
from my contour slices...
figuring the ground level at 103', I get 880 yards of boulder sticking up above ground.
I get 880 cu. yards
volume between two surfaces?
make a the lower half a surface and the upper half a surface then get the volume between them. Like a fill calculation.
The other way would be to make cross-sections, get the areas and do an old-fashioned mass diagram in Excel.