[GRASS-dev] GSOC Horizons and Stratigraphy

Benjamin Ducke benducke at fastmail.fm
Tue Jun 25 01:18:05 PDT 2013

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.


> Tim
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Dr. Benjamin Ducke, M.A.
{*} Geospatial Consultant
{*} GIS Developer

   benducke at fastmail.fm

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