Original and Progress Topo

Hi, 

I am using, getting used to rather, Kubla Cubed 2019 Pro.  I have a 36AC plot of land.  Original data of the land was obtained by manually shooting coordinates.  I have approximately 1200 points in the original topo.  Work started to mine the dirt material for embankment construction of a levee.  Since work started, a drone survey was completed of the area to obtain progress volumes.  This is my question:

I will use the software to build the progress survey using a compressed drone fine of approximately 6000 points.  
I will use the original data, approximately 1200 points, to build the original surface.  
When I use the "feature surface" option to create these two surfaces and calculate the volume of excavation, does the software only triangulate between the 1200 points in the original survey?  I'm concerned that I might not be capturing all of the features of land that are present at the site.  

I hope the above makes sense to you professionals.  I'm just getting started with this but would love to keep going as the benefit is immense.  

Than you for your help.  

Bo

Hi Bo

Welcome to the forums. 

Without seeing the project it is a bit difficult to diagnose exactly what the issue is, although I would guess that what is happening is that you have used the automatic outline when creating the existing feature surface around your 1200 surveyed points. 

It sounds like your proposed surface created with your drone survey is then larger than this existing surface.  Cut\Fill will not be calculated in areas where there is proposed and no existing so it is important to ensure there is enough existing to calculate against.  Instead of using the automatic outline on your existing survey surface which uses a 'shrink wrap' algorithm I would suggest using an extrapolate outline and manually tracing an area larger enough to encompass your proposed.   The below image demonstrates the issue, in both examples the proposed is the same, but in the second example there is not enough existing surface to calculate against so the cut\fill is very different.  This of course can be beneficial in some circumstances if you want to restrict the calculation only to a specific area (although using volume regions would be superior in most circumstances but it is still and effective technique which is used).

   

Let me know if this isn't the issue.   If you have screenshots you can upload them into a post.  It's a tricky you need to upload and then click 'add attachment' and then you can insert it into the post.  This video also might be helpful as it discusses the different outline types of a feature surface.  The automatic outline actually creates a 'varying levels' outline by default.  

Understanding Feature Surface Outlines

Hey Ted,

Thank you so much for your reply. I am indeed using the Automatic Outline to generate the original surface. I can most certainly start using the extrapolating feature to create the outline and encompass the area to make sure both original and progress are the same.

This is, however, what is troubling me: I have more points in the progress section than in the original. So the question is, does the software calculate the volume between the two layers? Or does the software "reduce" the number of points in the progress and calculates those against the points in the original? Say I have 1200points in the original and 6000points in the progress. Does the software take 6000 points, reduce to 1200points and then calculates the volume by triangulating between the same amount of points? I hope I'm making sense. I am concerned that I can be missing some ground features if the software reduces the progress to the amount of points in the original survey . I'll load the project as asked, but I don't think it will communicate the issue that I have in my mind.

Thanks for your help.

Bo

Hey Ted,

Thank you so much for your reply. I am indeed using the Automatic Outline to generate the original surface.  I can most certainly start using the extrapolating feature to create the outline and encompass the area to make sure both original and progress are the same. 

This is, however, what is troubling me:  I have more points in the progress section than in the original.  So the question is, does the software calculate the volume between the two layers?  Or does the software "reduce" the number of points in the progress and calculates those against the points in the original?  Say I have 1200points in the original and 6000points in the progress.  Does the software take 6000 points, reduce to 1200points and then calculates the volume by triangulating between the same amount of points?  I hope I'm making sense.  I am concerned that I can be missing some ground features if the software reduces the progress to the amount of points in the original survey . I'll load the project as asked, but I don't think it will communicate the issue that  I have in my mind. 

Thanks for your help.

Bo

The simple answer is : there is no loss of detail in the proposed model due to the existing model having less points.  For a longer answer read on :  

Kubla Cubed does not use the points to compute a volume calculation directly.  It completes a calculation in the following way using our propriety volumetric calculation engine - Kubla Kingdom. 

Step 1: Building the Ground TIN and Proposed TIN

Both the ground point elevation features (in your scenario point levels) and proposed elevation features are turned into two separate TINS (Triangulated Irregular Networks).  Basically, you end up with two surfaces made up of triangles.  The more points you have the more triangles. 

These TINS are calculated independently of each other using a Delauney triangulation algorithm. The lower detail existing will not affect a higher detail proposed and vice versa.  You will end up with more triangles in the more detailed surface.   So at the end of this step you end up with two TINS with potentially different triangle counts. 


Step 2 : Merging the TINS 

The next stage is to merge these two triangulations, to create a third triangulation which contains all the edges of the original triangulations.  This will be used to perform the calculations, and merging the two input triangulations means that every detail of both the existing and the proposed will be included in the calculations.  This is the basis of this method’s accuracy.

   

In the above merged calculation mesh, the flat area which could possibly be represented by just two triangles, actually has 100's as it has all the triangles of the ground mesh stamped into it.  However the topography remains the same.


Step 3 : Calculating Volumes 

The last stage is to calculate the cut and fill of each triangle on the merged calculation mesh.  The existing and proposed levels can be looked up from the TINS.  These values can be used to calculate the cut and fill for each prism, and the total volumes are easily obtained by adding all the prism volumes together. 

There is a lot of additional complexity to this method, in practice and our implementation has a lot of complexity additional to this but this is the basic principle. 

This method (and varieties of it) are described as the TIN Prism Volume method it is unlike the grid and cross section methods as it does not need a ‘level of detail’.

Due to the great complexity of these calculations and the thousands of triangles that are generated it is not practical to calculate triangular prisms by hand.  Instead, these calculations are done with specialised software like Kubla Cubed on powerful CAD workstations.  However, it should be noted that not all earthworks software uses this method; some software calculations are based on automated high-density grid calculations or the cross section method used in conjunction with TINS.  There are a few different methods out there in the wild.  The TIN Prism Volume is the most accurate mathematical solution but perhaps hardest to implement.  

Beautiful!!!! Thank you so much!!!

Bo