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I have a 3-D point shapefile of a geological fault dataset consisting of x,y, and z columns. I need to create a raster dataset from this point dataset. I have been trying to do this in ArcGIS; however, ArcGIS does not do this correctly as the dataset result is a vertical surface as opposed to a horizontal one. I.e. x, y does not change but z does.

For example: 

x,            y,           z
358749        5997833      270
358749        5997833      280

Is there a way I could flip the data (to make x,y horizontal and re-flip back to vertical afterwards) so that it can be interpolated?

Thanks in advance

PolyGeo
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user1655130
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2 Answers2

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A 2D GIS like QGIS is not adequate for this sort of thing. You need a 3D GIS like GRASS GIS (free) or ArcGIS with 3D extensions, Python scripting (see for example Is there are QGIS plugin to allow the 3d visualisation of geological borehole data similar to the functionality of Target for ArcGIS?) or specialized geological modelling software like GoCAD.

With the 3D view of GRASS GIS, you can see the problem (geological fault and layers interpolated -> the blue fault surface is a line in 2D, as the yellow, green layers and the red fault from a geological map).

enter image description here

What you want to do is a simple 90 degrees anticlockwise 3D rotation around the x axis, thus
`y'= z and x'= x

But after, you need to rotate clockwise the resulting raster again and -> a line in QGIS...

Community
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gene
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  • Ok thanks, I tried the following: Z=inverse(y), X=inverse(X) but this did not work. Is this what you mean? Thanks again – user1655130 Jun 25 '13 at 16:42
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This is something I ran into with ArcGIS. If you use 3D analyst you can add a point and extrude it to the lower depth. If you fudge the 2nd point's x or y value by .00001 ArcGIS will see it as a seperate point value for your line and let you actually generate the vertical line. It will have a very slight offset but that .00001 value is negligible in the overall display. You can use a larger decimal (.1, .01, .001, etc.) depending on your map units.

The bottom line that I've experienced (no pun intended) is that generating a perfectly vertical line from coordinates doesn't work as simple as you'd expect in ArcGIS . You can extrude a point to depth, you can edit a line in 3D, or you can offset an x or y value ever so slightly.

user19436
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