[GRASS-dev] GSOC Horizons and Stratigraphy

Pierre Roudier pierre.roudier at gmail.com
Wed Jun 26 10:00:09 PDT 2013

Hi Benjamin,

As far as soils data, we would probably often mask with depths min or
max, use a plan to cut the profile collection to return points ("give
the carbon value at 13.5cm depth for this collection of profiles").

Alternatively, we would try to interpolate a profile collection to
harmonise soil depths: while data is usually collected on
heterogeneous depths intervals, one might want to harmonise the
collection for quantitative analysis: for example the new depth
support might be {0-5cm, 5-10cm, 10-30 cm, 30-60cm, 60-100cm}.

Just 2 cents,


2013/6/25 Benjamin Ducke <benducke at fastmail.fm>:
> On 06/25/2013 10:00 AM, Tim Bailey wrote:
>> Hi Ben,
>> All that I meant by mask is, in this case,  an r3 map that defines a
>> subset of space that subsequent operations are constrained to. I guess I
>> was just expressing worry about creating runaway data demands.The region
>> settings act as a three dimensional bounding cube, does not seem
>> adequate to constrain a tiling scheme with relatively sparse data.In the
>> compromise scenario that Dylan suggested with 10 meter xy and 1 cm z
>> resolution and 1 meter depth we would be looking at populating 10000
>> voxels per hectare for a flat landscape. However if we were using a
>> simple bounding box to define the region and we had 5 meters of relief
>> we would end up with 50000 or 60000 voxels. As the area of coverage gets
>> bigger cost of the range in z values gets worse.
> That's a good point that I hadn't thought about.
> Clearly, we don't want the interpolation to go
> beyond the limits of the terrain surface. It would
> probably be a good idea for the user to be able to
> supply an additional DEM input that could supply
> upper cut-off values. A lower cut-off could simply
> be defined as a constant depth value, and the same
> for the extents along the X-Y plane. Apart from that,
> the interpolator should use a configurable search
> radius for points, so that it won't start interpolating
> values in areas that have no sample data.
> Ben
>> Tim
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> --
> Dr. Benjamin Ducke, M.A.
> {*} Geospatial Consultant
> {*} GIS Developer
>   benducke at fastmail.fm
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Landcare Research, New Zealand

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