We are building on a slight slope: I have come to realise that this is a significant advantage in terms of drainage and other issues.

 

Talking to a contractor about how much stone will be brought in, he mentioned that it was something of an art to estimate the amount of stone needed - especially where there's a slope.

From my teaching background I know that conservation of volume is one of the last things that humans learn (look at the difference in the designs of pint glasses - some look large, others surprisingly small - even experienced people find it hard to estimate volume)

 

We have had a topographical survey. I have superimposed the piling mat area in red.

 

The image is oriented North-South. You will see there's a cross-fall South East - North West of about a meter. And somewhat less from the North East to the South West. 

 

Roughly, it's a lop-sided wedge. If it were a simple wedge, calculating the volume would be easy. But it isn't a simple wedge.

I frightened myself silly looking at maths websites in attempt  to calculate the volume.

 

I already hear a chorus from over the water about over-thinking. This is just a bit of fun. At worst we'll need a few more loads of stone: tough, suck it up.

 

I'm interested in how to go about calculating that wonky wedge volume. 

Pointers, please!

Draw it up on the CAD and get that to work it out.

One method would be to use statistics i.e. take cross sectional measurements at fixed/known points and get the mean length/width/depth.

I think you can also use vectors to help with the estimation.

 

Rotating it may help too.

Make a little scale model from plastacine and drop into a bucket of water...

36 minutes ago, recoveringacademic said:

If it were a simple wedge, calculating the volume would be easy. But it isn't a simple wedge.

 

If I've read that right, it's estimating the area of the wedge you are struggling with, but estimating the average slop across the area you are OK with.

 

If so use Google Maps. Switch to satellite view, right mouse click in one corner of the area and trace around the lopsided wedge shape. When you click back on to where you started it will give you the area (as well as the circumference).

 

Then multiply this by the average depth.

Edited January 12, 20179 yr by IanR

You can get elevation on Google Earth too, not sure at what resolution.

https://support.google.com/earth/answer/148134?hl=en

1 minute ago, SteamyTea said:

You can get elevation on Google Earth too, not sure at what resolution.

https://support.google.com/earth/answer/148134?hl=en

 

Which you can import to Sketchup (Google Earth topology), but if it's a constant slope you should be able to estimate the average depth "fairly" accurately.

Seems pretty good too.

 

Edited January 12, 20179 yr by SteamyTea
Trying to remove duplicate image

I realise you are trying to do it accurately just for the fun of the exercise. But if I was trying to do it on site I would try to get it into as many cuboid's and right angled wedges as possible and add them together. Then whatever's left give it a generous guesstimate.  

If you have school children to hand the fun and educational way is to peg it out on the ground and estimate it by using known size cardboard boxes e.g. MOrrissons banana boxes, compare with a calculation in class. You can just have a small number and lay them next to each other in sequence.

 

For the other. I reckon a number to 2-3% i.e. less than one lorryload is adequate, but a better estimate should be straightforward.

 

Obv. the area is easy ... just draw a diagonal and use Pythagoras twice for the length or measure off on your software, then the formula for the area of a scalene triangle on each of the two parts.

 

I would deal with the dual aspect slope by approximating the sw ne 18cm fall to zero as the other way is 10x larger, and averaging the se nw slope at height 26.9 which is exactly half.

 

I would allow a bit extra by making that 26.9 into perhaps 26.8 or rounding up by x lorryloads (= say 10cm / approx depth * no of lorryloads estimated) to make sure I was slightly over in my budget calcs. Then I would want somewhere to use any excess close by and an option to vary my order by plus or minus 5%.

 

I would also do a couple of sanity checks on the ground if I felt it necessary.

 

If you have a pro ground survey, I would expect your surveyor can draw a box and press a button on his software.

 

Or you can set up some posts and a tarpaulin and measure the amount of water it take to fill to the new level .

 

Ferdinand

Edited January 12, 20179 yr by Ferdinand

PS The google earth gradient feature is a fantastic tip.

Whoooaaa! Lots here to distract me from the nitty gritty of the Windows  Schedule. Thanks for the excuse. 

Draw it as a solid in AutoCAD;

 

1) EXTRUDE THE plan

2) Draw the "wedge" and EXTRUDE that

3) SUBTRACT wedge from the solid 

4) Use MASSPROP to determine the volume.

 

 

 

@Onoff, thanks.  I'll need that later set of commands later when I get my hands on a copy of AutoCAD. I have DWGTrue View. This appears far too interesting to me to let software do it for me. I'll try steam first and then see if the software gets it 'right'

2 hours ago, IanR said:

[...]

If so use Google Maps. Switch to satellite view, right mouse click in one corner of the area and trace around the lopsided wedge shape. When you click back on to where you started it will give you the area (as well as the circumference).

 

Then multiply this by the average depth.

 

Bingo! Even I can do it!

Simple things make my day sometimes!

Right, can't wait to see that contractor again...... I am so going to enjoy the conversation....

3 hours ago, recoveringacademic said:

Right, can't wait to see that contractor again...... I am so going to enjoy the conversation....

 

I'm sure he can't wait! 

Edited January 12, 20179 yr by jack
Edited to delete drawing accidentally posted - the google maps idea was much better than what I came up with!

BTW any quadrilateral can be thought of as 2 triangles and if you want to calculate the area of a triangle, just google it   The easiest way is to measure the four sides and a diagonal; you can crank the numbers from this.   

I am always amazed by the knowledge on this site!  Is there anything you guys dont know?

3 hours ago, TheMitchells said:

Is there anything you guys dont know?

 

Why Faye tolerates me...... I think we're all lost on that one