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Calculating the volume of irregular surfaces and subsurfaces

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Hello all,

I am a new graduate student contemplating buying rockworks for a specific problem associated with my research, I wonder if someone here can tell me if this is a problem Rockworks can help with?

What I need to do is calculate the volumes of many (~100), small (<1km^3) volcanoes. The problem is that they are very densly spaced and many overlap one another. Im envisioning being able to use DEMs any any other xyz data I can get to make a 3D visualization and fit geometric cones of a known volume to the volcanic cones of a unknown volume. The hard part, in my opinion, will be interpolating how the slope of one volcano (we'll call it volcano A) extends underneath another (volcano B ) and thus subtracting that volume from the calculation of volcano B, so forth and so on for about 100 of these guys.

Does this sound like something I can build in Rockworks? Please let me know if Ive not explained myself very well, its rather hard to do with out a sketchbook.

Thank you,


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Hi Mandie,

You should be able to compute the volumes of the overlapping volcanic cones, using a surface topography grid model (created from DEMs or XYZ points) and individual polygon definitions for the each volcano base. You could digitize these polygons inside RockPlot2D from an imported map or other other digital image.

Basically you would run a Grid Polygon filter on the surface grid for each volcano, setting the nodes outside the polygon to a user-specified constant or to the elevations in another grid model. The clipped grid, which you could conceptualize as a table top with the volcano sticking up, could be run through the Grid Statistics Report to determine volume.

The grid clipping and statistics reporting process could be batched for each cone using RCL commands. Unfortunately, the polygons would need to be defined by hand.

Where the volcanoes overlap, you would need to be sure that the polygons don't overlap (and produce overlapping volumes) or, for more complicated sub-surface models, you could use Boolean (true/false) grid models to zero-out nodes from one surface where they overlap the other. (Right about now I'm also feeling the need for a sketchbook...)

Feel free to pursue this with more specific details by email.

Molly Mayfield

RockWare Inc

[email protected]

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