raster3dintro(1grass) [debian man page]

raster3dintro(1grass)						Grass User's Manual					     raster3dintro(1grass)

3D Raster data (voxel) in GRASS GIS
   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). Alter-
       natively, 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.

   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

       (C) 2008-2011 GRASS Development Team

GRASS 6.4.2														     raster3dintro(1grass)

projectionintro(1grass) 					Grass User's Manual					   projectionintro(1grass)

NAME

       projectionintro - Projections and spatial transformations

       Projections and spatial transformations

Projections and spatial transformations in GRASS GIS
   Introduction
       A  GRASS  location is referenced with a single projection and coordinate system (or unreferenced as XY location). When creating a new loca-
       tion from an existing raster or vector map using the tools available from the startup screen or the map	import	commands,  projection  and
       coordinate  system  are defined.  To change the projection of maps, a new location has to be created and the desired maps have to be repro-
       jected into it from the source location as explained below.

   Raster map projections
       Raster maps are backward projected in GRASS. This means that the user has to run the raster projection command (r.proj) in the target loca-
       tion and "pull" the map from the source location.  Both locations need to have a projection defined.

   Raster map transformation
       To  transform  an  unprojected  map from a XY location into a projected location (or another XY location), a forward transformation is per-
       formed.	The unreferenced map is geocoded within the XY location by defining four corner points or by seeking several ground control points
       (i.target,  i.points)  and  then  transformed into the target location (i.rectify). Polynomial transformation of 1st, 2nd and 3rd order are
       supported.

       A graphical user interface is provided by gis.m.

       To simply translate a raster map (without stretching or rotation), the r.region command can be used.

   Vector map projections
       Vector maps are backward projected in GRASS. This means that the user has to run the vector projection command (v.proj) in the target loca-
       tion and "pull" the map from the source location.  Both locations need to have a projection defined.

   Vector map transformation
       To  transform  an unprojected map (e.g. CAD map) into projected coordinates, a forward transformation is performed. The unreferenced map is
       imported into the location with projection and geocoded within this location by defining  four corner points or by seeking  several  ground
       control points.	These points are stored into an ASCII file and then transformed within the same location (v.transform).

       A graphical user interface is provided by gis.m.

   References
		      ASPRS Grids and Datum

		      Projections Transform List (PROJ4)

		      MapRef - The Collection of Map Projections and Reference Systems for Europe

		      Information and Service System for European Coordinate Reference Systems - CRS

   See also
		     Introduction to GRASS raster map processing

		     Introduction to GRASS image processing

		     Introduction to GRASS vector map processing

       full index

       (C) 2008-2011 GRASS Development Team

GRASS 6.4.2														   projectionintro(1grass)