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
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-- Dr. Benjamin Ducke, M.A. {*} Geospatial Consultant {*} GIS Developer bendu...@fastmail.fm _______________________________________________ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev