3D Raster data (voxel) in GRASS GIS¶
GRASS GIS is one of the few GIS software packages with volume data support. Here
data are stored as a 3D raster with a unit volume called a voxel (volume
pixel). Voxels are designed to support representations of trivariate
continuous fields.
3D Raster (voxel) import¶
The module r3.in.ascii supports generic x,y,z import. Alternatively, voxels can
be generated from 3D point vector data (v.to.rast3). Always the full map is
imported. Volumes can also be created based on 2D elevation map(s) and value
raster map(s) (r.to.rast3elev). Alternatively, a volume can be composed of
several 2D raster map slices which are merged into one 3D raster volume map
(r.to.rast3).
Voxel region settings and 3D MASK¶
GRASS 3D raster map processing is always performed in the current 3D region
settings (see g.region,
-p3 flags), i.e. the current region extent,
vertical extent and current 3D resolution are used. If the 3D resolution
differs from that of the input raster map(s), on-the-fly resampling is
performed (nearest neighbor resampling). If this is not desired, the input
map(s) has/have to be reinterpolated beforehand with one of the dedicated
modules. Masks can be set (r3.mask).
Voxel operations¶
Powerful 3D map algebra is implemented in r3.mapcalc. A 3D groundwater flow
model is implemented in r3.gwflow.
Voxel conversion to vector or 2D raster maps¶
3D vector point data can be converted to a GRASS 3D raster map (v.to.rast3).
Layers from a 3D raster map can be converted to a 2D raster map (r3.to.rast).
Cross sectional 2D raster map can be extracted from 3D raster map based on a
2D elevation map (r3.cross.rast).
Voxel statistics¶
Volume statistics can be calculated with r3.stats and r3.univar.
Voxel interpolation¶
From 3D vector points, GRASS 3D raster maps can be interpolated (v.vol.rst).
Results are volumes, or 2D raster maps can be also extracted.
Voxel export¶
GRASS 3D raster maps can be exported to VTK (r3.out.vtk). VTK files can be
visualized with the
VTK Toolkit,
Paraview and
MayaVi.
GRASS 2D raster maps can be exported to VTK with r.out.vtk, GRASS vector maps
can be exported to VTK with v.out.vtk.
Alternatively, GRASS 3D raster maps can be imported and exported from/to Vis5D
(r3.out.v5d). Note that Vis5D is limited in the number of supported voxels.
Finally, export to 3D ASCII is also available (r3.out.ascii).
See also¶
Introduction to GRASS raster map processing
full index
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