r3: replace occurences of volume, voxel and 3D grid by 3D raster in introduction page

 * discussion for the names included
 * minor clean up of import and export sections
 * some 'GRASS' to 'GRASS GIS'
 * 3D visualization and temporal to see also
 * short data types description provided
 * unclear how to change note about Vis5D


git-svn-id: https://svn.osgeo.org/grass/grass/trunk@64053 15284696-431f-4ddb-bdfa-cd5b030d7da7

raster3d/raster3dintro.html

@@ -1,42 +1,93 @@
-<!-- meta page description: 3D raster data (voxel) processing in GRASS GIS -->
+<!-- meta page description: 3D raster data in GRASS GIS -->
 <!-- meta page index: raster3D -->
-<h3>3D Raster maps (voxels) in general</h3>
+<h3>3D raster maps in general</h3>
 
-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. The vertical dimension supports spatial and temporal units.
-Hence space time voxel cubes with different temporal resolutions can be created and processed.
-<p>
+GRASS GIS is one of the few GIS software packages with 3D raster data support.
+Data are stored as a 3D raster with 3D cells of a given volume.
+3D rasters are designed to support representations of
+trivariate continuous fields.
+The vertical dimension supports spatial and temporal units.
+Hence space time 3D raster with different temporal resolutions
+can be created and processed.
 
+<p>
 GRASS GIS 3D raster maps use the same coordinate system as
 2D raster maps (row count from north to south) with an additional z dimension (depth)
-counting from bottom to top. The upper left corner (NW) is the origin of the voxel. 
-Volumes are stored using a tile cache based approach. This allows abritrary read 
-and write operations in the created volume. The size of the tiles can be specified at import time
-with <a href="r3.in.ascii.html">r3.in.ascii</a> or the data can be retiled using
+counting from bottom to top. The upper left corner (NW) is the origin. 
+3D rasters are stored using a tile cache based approach. This allows arbitrary
+read and write operations in the created 3D raster. The size of the tiles
+can be specified at import time with a given import module such as
+<a href="r3.in.ascii.html">r3.in.ascii</a> or the data can be retiled using
 <a href="r3.retile.html">r3.retile</a> after import or creation.
 
 <div align="center" style="margin: 10px">
 <img src="r3_volume_layout.png" border=0><br>
-<i>The volume coordinate system and tile layout of the RASTER3D library</i>
+<i>The 3D raster map coordinate system and tile layout of the RASTER3D library</i>
 </div>
 
-<h3>3D Raster (voxel) import</h3>
+<h3>Terminology and naming</h3>
+
+GRASS GIS uses terminology where continuous 3D data represented by regular grid
+or lattice is called <em>3D raster map</em>.
+3D raster map works in 3D in the same as (2D) raster map in 2D,
+so it is called the same except for the additional 3D.
+Some literature or other software may use terms such as 3D grid, 3D lattice,
+3D matrix, 3D array, volume, voxel, voxel model, or voxel cube.
+Note that terms volume and volumetric often refer to measuring
+volume (amount) of some substance which may or may not be related to 3D rasters.
+
+Note that GRASS GIS uses the term 3D raster map or just 3D raster for short,
+rather than 3D raster layer because term map emphasizes
+the mapping of positions to values which is the purpose of 3D raster map
+(in mathematics, map or mapping is close to a term function).
+While the term layer emphasizes overlaying or stacking up.
+The former is not the only only operation done with data
+and the latter could be confusing in case of 3D raster data.
+
+3D raster map is divided into cells in the same as the (2D) raster map.
+A cell is a cuboid or cube depending on the resolution.
+The resolution influences volume of one cell.
+Some literature or other software may use terms such as volume, volume unit,
+volumetric pixel, volume pixel, or voxel.
+Note that voxel can be sometimes used to refer to a whole 3D raster
+and that for example in 3D computer graphics, voxel can denote object
+with some complicated shape.
+
+Type of map and element name in GRASS GIS is called <code>raster_3d</code>.
+The module family prefix is <code>r3</code>.
+Occasionally, for example in Python, 3D raster related things can be
+referred differently, for example according to a programming language standards.
+
+In GRASS GIS 3D rasters as stored in tiles which are hidden from user most
+of the time. When analyzing or visualizing 3D rasters user can create
+slices or cross sections. Slices can be horizontal, vertical, or general
+plains going through a 3D raster. Slices, especially the horizontal ones, may be
+called layers in some literature or some other software.
+Cross sections are general functions, e.g. defined by 2D raster, going through
+a 3D raster.
+
+When 3D raster is used in the way that vertical dimension represents time
+3D raster can be referred to as space time cubes (STC) or space time cube
+3D raster. Some literature may also use space time voxel cube,
+space time voxel model or some other combination.
+
+<h3>3D raster import</h3>
 
 The modules <a href="r3.in.ascii.html">r3.in.ascii</a> and
  <a href="r3.in.bin.html">r3.in.bin</a> supports
-generic x,y,z ASCII and binary array import. Alternatively, volumes can be generated
+generic x,y,z ASCII and binary array import.
+Alternatively, 3D rasters can be generated
 from 3D point vector data (<a href="v.to.rast3.html">v.to.rast3</a>). 
 Always the full map is imported.
-Volumes can also be created based on 2D elevation map(s) and value raster map(s)
+3D raster can also be created based on 2D elevation map(s) and value raster map(s)
 (<a href="r.to.rast3elev.html">r.to.rast3elev</a>). Alternatively,
-a volume can be composed of several 2D raster map slices which are
-merged into one 3D raster (voxel) map (<a href="r.to.rast3.html">r.to.rast3</a>).
+a 3D raster can be composed of several 2D raster maps.
+2D rasters are considered as slices in this case and
+merged into one 3D raster map (<a href="r.to.rast3.html">r.to.rast3</a>).
 
 <h3>3D region settings and 3D MASK</h3>
 
-GRASS 3D raster map processing is always performed in the current 3D region
+GRASS GIS 3D raster map processing is always performed in the current 3D region
 settings (see <a href="g.region.html">g.region</a>, <em>-p3</em> 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),
@@ -45,54 +96,67 @@ 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 (<a href="r3.mask.html">r3.mask</a>).
 
-<h3>Volume operations</h3>
+<h3>3D raster analyses and operations</h3>
 
-Powerful 3D map algebra is implemented in <a href="r3.mapcalc.html">r3.mapcalc</a>.
+Powerful 3D raster map algebra is implemented in
+<a href="r3.mapcalc.html">r3.mapcalc</a>.
 
 A 3D groundwater flow model is implemented in <a href="r3.gwflow.html">r3.gwflow</a>.
 
 <h3>3D raster conversion to vector or 2D raster maps</h3>
 
-3D vector point data can be converted to a GRASS 3D raster map
-(<a href="v.to.rast3.html">v.to.rast3</a>).
-Layers from a 3D raster map can be converted to a 2D raster map
+Slices from a 3D raster map can be converted to a 2D raster map
 (<a href="r3.to.rast.html">r3.to.rast</a>).
 Cross sectional 2D raster map can be extracted from 3D raster map based
 on a 2D elevation map (<a href="r3.cross.rast.html">r3.cross.rast</a>).
 
 <h3>3D raster statistics</h3>
 
-Volume statistics can be calculated with <a href="r3.stats.html">r3.stats</a>
+3D raster statistics can be calculated with <a href="r3.stats.html">r3.stats</a>
 and <a href="r3.univar.html">r3.univar</a>.
 
 <h3>3D raster interpolation</h3>
 
 From 3D vector points, GRASS 3D raster maps can be interpolated
-(<a href="v.vol.rst.html">v.vol.rst</a>). Results are volumes,
-or 2D raster maps can be also extracted.
+(<a href="v.vol.rst.html">v.vol.rst</a>).
+Results are 3D raster maps, however 2D raster maps can be also extracted.
 
 <h3>3D raster export</h3>
 
 The modules <a href="r3.out.ascii.html">r3.out.ascii</a> and
- <a href="r3.out.bin.html">r3.out.bin</a> support the export of
- 3D raster maps as ASCII or binary files. The output of these modules
- can be imported with the coresponding import modules noted above.
+<a href="r3.out.bin.html">r3.out.bin</a> support the export of
+3D raster maps as ASCII or binary files. The output of these modules
+can be imported with the corresponding import modules noted above.
+
 <p>
 NetCDF export of 3D raster maps can be performed using the module 
 <a href="r3.out.netcdf.html">r3.out.netcdf</a>. It supports 3D raster maps
-with spatial and temporal vertical dimension (Space time voxel cubes).
+with spatial dimensions and temporal (vertical) dimension.
+
 <p>
-GRASS 3D raster maps can be exported to VTK (<a href="r3.out.vtk.html">r3.out.vtk</a>).
+GRASS GIS 3D raster maps can be exported to VTK
+using <a href="r3.out.vtk.html">r3.out.vtk</a>.
 VTK files can be visualized with the 
-<em><a href="http://www.vtk.org">VTK Toolkit</a></em>, 
-<em><a href="http://www.paraview.org">Paraview</a></em> and 
+<em><a href="http://www.vtk.org">VTK Toolkit</a></em>,
+<em><a href="http://www.paraview.org">Paraview</a></em> and
 <em><a href="http://mayavi.sourceforge.net">MayaVi</a></em>.
-GRASS 2D raster maps can be exported to VTK with <a href="r.out.vtk.html">r.out.vtk</a>,
-GRASS vector maps can be exported to VTK with <a href="v.out.vtk.html">v.out.vtk</a>.
+Moreover, GRASS GIS 2D raster maps can be exported to VTK with
+<a href="r.out.vtk.html">r.out.vtk</a>
+and GRASS GIS vector maps can be exported to VTK with
+<a href="v.out.vtk.html">v.out.vtk</a>.
+
 <p>
 Alternatively, GRASS 3D raster maps can be imported and exported from/to Vis5D
 (<a href="r3.in.v5d.html">r3.in.v5d</a>, <a href="r3.out.v5d.html">r3.out.v5d</a>).
 Note that Vis5D is limited in the number of supported volumes.
+<!-- it is not clear what 'volume' means here -->
+
+
+<h3>3D raster data types</h3>
+
+3D raster's single-precision data type is most often called "FCELL" or "float",
+and the double-precision one "DCELL" or "double".
+
 
 <h3>See also</h3>
 
@@ -100,6 +164,8 @@ Note that Vis5D is limited in the number of supported volumes.
   <li><a href="rasterintro.html">Introduction into raster data processing</a></li>
   <li><a href="vectorintro.html">Introduction into vector data processing</a></li>
   <li><a href="imageryintro.html">Introduction into image processing</a></li>
-  <li><a href="databaseintro.html">Database management</a></li>
+  <li><a href="temporalintro.html">Temporal data processing</a></li>
   <li><a href="projectionintro.html">Projections and spatial transformations</a></li>
+  <li><a href="wxGUI.nviz.html">wxGUI 3D View Mode</a></li>
+  <li><em><a href="m.nviz.image.html">m.nviz.image</a></em></li>
 </ul>