[GRASS-user] r3.in.xyz

[Moritz Lennert]

François,

First of all, I meant r.to.rast3elev [1], not r.to.rast3. Sorry for the 
mixup.

On 09/07/18 15:17, Francois Chartier wrote:
> Thanks moritz.  I will try this. I have about 300 m of elevation to 
> interpolate so i might group by thickness bands of 2 metres etc.
> Is there a way i can make a batch mode where i prep all the xy p by 
> elevation and then interpolate automatically onw after another all slices?

I'm not sure what you mean by grouping by thickness bands.

IIUC your data, you have a series of boreholes. For a given geological 
layer you have its top elevation at each borehole where this layer is 
encountered. Just interpolate these top elevations for each geological 
layer. This gives you an elevation map per geological layer.

Then you can use r.to.rast3elev to create a 3D map.

One issue I've observed in my (limited) experience with this module is 
the need to define relevant vertical region values (resolution and top 
and bottom limits). If the resolution is larger than the actual layer 
thickness, the result will obviously not be satisfying.


Moritz

[1] https://grass.osgeo.org/grass74/manuals/r.to.rast3elev.html


> 
> On Mon, Jul 9, 2018, 03:01 Moritz Lennert, <mlennert at club.worldonline.be 
> <mailto:mlennert at club.worldonline.be>> wrote:
> 
>     Le Sun, 1 Jul 2018 13:27:03 -0400,
>     Francois Chartier <fra.chartier at gmail.com
>     <mailto:fra.chartier at gmail.com>> a écrit :
> 
>      > Hi,
>      >
>      > I am reposting the initial question:
>      >
>      > “I am working with a data set that consists of borehole logs with a
>      > Top of a layer (layer 1) and the top of the underlying layer (layer
>      > 2) (which is also the bottom of the overlying layer 1).  Everything
>      > in between the elevation of top of layer 1 and top of layer 2
>      > correspond to a Layer 1 property.
>      >
>      > The thickness of Layer 1 varies and this layer may not exist
>      > everywhere (pinches out).  Above the Layer the property is different;
>      > in other words the property only starts below the Top of layer 1
>      > until the underlying Top of the next layer. Not sure of the
>      > capabilities of the interpolation in Grass and working with a very
>      > large data set (i cannot link every top of layers together), my first
>      > approach was to create a each Layer property for every elevation
>      > slice along each Borehole axis, interpolating soil properties at
>      > every elevation between Boreholes.
>      >
>      > The key question is can v.vol.rst (changed this from r3.in.xyz
>     <http://r3.in.xyz>)
>      > interpolate in 3D without a Property at every elevation slice,
>      > • while respecting the condition that above the Top of the layer 2,
>      > the property corresponds to the Overlying top layer 1, and
>      > • that the property is continuous until the next underlying layer 3 -
>      > can someone confirm this? To provide a bit of background, borehole
>      > data bases, identify the top of layer as encountered when drilling
>      > downwards, and provide the elevation of the next layer (pick); in
>      > between the soil property is the same, however there is no data
>      > points.  When interpolating, while there is no data point in between
>      > the two geological picks, the property should still have weight in
>      > the interpolation process.”
>      >
> 
>     v.vol.rst is a tool to interpolate a continuous value into a 3D space.
>     So, I do not think that it is the tool you are looking for.
> 
>     As already mentioned before:
> 
>      > You probably want to use something like r.to.rast3. This would mean
>      > interpolating each layer separately into 2D elevation maps and then
>      > assemble them into 3D using r.to.rast3.
> 
>     Have you tried this approach ?
> 
>     Moritz
>