[GRASS-user] r3.in.xyz

Sun Jul 1 10:27:03 PDT 2018

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) 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.”

Thank You 

Sent from Mail for Windows 10

From: Vaclav Petras
Sent: June 28, 2018 8:27 PM
To: Francois Chartier
Cc: Moritz Lennert; GRASS user list
Subject: Re: [GRASS-user] r3.in.xyz

Hi, I'm not following this discussion fully, but don't you need just r.to.rast3elev followed by some raster algebra with ifs (r3.mapcalc)?

https://grass.osgeo.org/grass74/manuals/r.to.rast3elev.html
https://grass.osgeo.org/grass74/manuals/r3.mapcalc.html

Best,
Vaclav

On Thu, Jun 28, 2018 at 12:18 PM, Francois Chartier <fra.chartier at gmail.com> wrote:
Is it possible to define a horizontal constraints so that more weight is given on the interpolation of the property horizontally rather than vertically. 
Similarly in kriging we can define a semi variogram with an orientation in 2d, and i would like to know if it can be done in 3d.  
Also what about the question regarding the elevations between the top and bottom of the soil formation.  Is there a possibilty for v vol rst to consider data points in between top and bottom.

On Jun 28, 2018 03:40, "Moritz Lennert" <mlennert at club.worldonline.be> wrote:
On 27/06/18 16:32, Francois Chartier wrote:
> So therefore, my approach of generating a soil property at each 
> elevation and interpolating is a correct approach.
> Is there a way that i can constrain the interpolation horizontally. 
Not sure what you mean by constraining the interpolation horizontally.

You can create a 2D elevation map by interpolating all your height 
information of layer 1 (for example using v.surf.rst). Then you create a 
second elevation map interpolating the layer 2 height information, etc.

Moritz

> I. 
> Cant remember the module name i am using but i am generating the 3d 
> raster from the 3d data points directly.
> 
> 
> On Tue, Jun 26, 2018, 23:38 Moritz Lennert, 
> <mlennert at club.worldonline.be <mailto:mlennert at club.worldonline.be>> wrote:
> 
>     On 27/06/18 03:59, Francois Chartier wrote:
>      > Hi,
>      >
>      > 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.
>      >
>      > I read on another forum that r3.in.xyz <http://r3.in.xyz>
>     <http://r3.in.xyz> can
>      > 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.
>      >
> 
>     I don't think r3.in.xyz <http://r3.in.xyz> is what you need. This

>     module aggregates 3D
>     point data into voxels.
> 
>     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.
> 
>     Moritz
> 

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