Scrap metal piles and volume calculations

Hope you all are well in these miserable times…

When the snow melts away in may I’m supposed to do a volume measurement on one huge pile of scrap metal and an equally large pile containing waste (mostly shattered wood) from construction sites.
Both piles are on flat ground so I think Triangulated method should work just fine.

Is there anything I should think of? I mean: both piles are of low density with lots of air built in the piles.
Is there anthing I should adjust when capturing the images? How accurate is DD:s volume calculation.

I think I will compare DD:s calculations with Rhino to which I got a couple of excellent Python - scripts for volume calculations (among other possibilities). Thanks for that, @SolarBarn.

Any hint/link is appreciated.

You got one of the major factors. Look at about a square-meter of the pile and estimate how much of a percentage of airspace is there and back that out of what you get for the total. I like to note this new volume in the description of the annotation. If the pile is 48cy with 10% air then put “Metal Scrap - 44cy”.

Just make sure you get as many angles of each pile as you efficiently can. Enhanced 3D with nadir and perimeter only should do the trick. Fly low at 50ft above the pile and make you perimeter big enough to capture the entire pile in the frame. Make sure to overfly if you don’t have a background image of where the piles are and/or use you location on the mobile device to establish the center.

We have found that with dense piles and well estimated loose piles that we typically get within 3-5%.

New questions…

Why do you prefer such a low altitude for the capture? I normal do my capture at a height 3 times the highest object.

Do you think triangulated mode will do the job? It’s so difficult to decide which method to use for a given pile.

Finally: What did you mean with “Make sure to overfly if you don’t have a background image of where the piles are and/or use you location on the mobile device to establish the center”?


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This is according to your case, such as the pile that have allot of airspace. The materials in your piles have allot of edges that will get lost as altitude increase and your pile will end up with too much volume. Dirt and aggregate type piles are fine to fly as high as 250ft then you start losing details on them.

I use triangulated for everything except when the material is up against a wall or I am trying to get the lowest point like benching a slope. I don’t see any advantage to a flat plane unless you are on a completely flat pad. If you put enough points triangulated will do the same thing. I actually wish triangulated was the default.

Just make sure you are capturing enough of the area. I have messed up a couple of times early on where I manually put the pile in the center of the frame and backed up to what I thought was the furthest part out and ended up not catching everything. Bonehead rookie mistake. You can use the GPS marker for your location to walk around the pile as you draw the perimeter, or you can do it with the drone, but why waste precious batteries?..

Thank you for your replies! I will certainly use them when the time has come to actually do the capturing.

On density/percentage air in the piles:
I’m not sure id I’m going to calculate the density of the piles. I think I’ll leave this for the customer as they’re only asking for the volume. My concern was about how correct the volume calculation is with this material (with lots of void built in the pile). A pile of sand is so dense that the calculation should be withing 3 - 5%, but a pile of scrap metal (or wood)?

On method to calculate volume
This is so confusing. I tend to use triangulated method on every pile I’ve measured so far. I’m also using LOTS of points surrounding the pile in question. As far as I can understand it gets more correct with increasing numbers of points.
I have never (luckily) having to measure a pile up against a wall. If this happends I will surely contact you again for some advise…:wink:

Thanks for your kind replies! Stay safe!


That’s what the airspace mention was about. The human brain can guesstimate pretty well what percentage of the overall shape might be air. The “Density” entry would only be used if they were selling by the ton and they gave you the factor and the cost (and wanted you to do that). Definitely not something I would keep up with without an ala carte charge.

Triangulation covers the vast majority of takeoffs except for what lowest-point is used for. I have also requested highest-point. As for the number of points there is a point :wink: of diminishing returns. Usually if you just capture the major angles it will make very little difference if you continue to add detail. You’ll learn how to efficiently get around the toe. This area has about 7% of fall from left to right…


Also make sure the Elevation layer is on. The coloring will give you a far better idea of where the actual levels are at. You can condense the color range to isolate the stockpile you are working on to use the full spectrum in that area. This is VERY helpful the more slope the site has and the bigger the stockpiles get.

Default Color Scale for the site

Condensed for the specific stockpile

Here’s more detail on the base planes if you hadn’t already seen it. The strength of traingulation is that it can make flat triangles and do what it was really intended for which is capture the tops and bottoms of each grade break or slope. Fear my paint skills!

Well… :slight_smile: To be honest: I didn’t get much out of the last drawing. …
But it doesn’t matter. I think I get it.