GRASS GIS: v.drape

NAME

v.drape - Convert 2D vector to 3D vector by sampling of elevation raster. Default sampling by nearest neighbor

KEYWORDS

vector

SYNOPSIS

v.drape
v.drape help
v.drape input=name [type=string[,string,...]] [rast=string] [method=string] output=name [--overwrite]

Flags:

--overwrite: Force overwrite of output files

Parameters:

input=name: Name of input vector map
type=string[,string,...]: Type; Options: point,centroid,line,boundary,face,kernel; Default: point,centroid,line,boundary,face,kernel
rast=string: Elevation raster for height extraction
method=string: Sampling method; Options: nearest,bilinear,cubic; Default: nearest; nearest: nearest neighbor; bilinear: bilinear interpolation; cubic: cubic convolution interpolation
output=name: Name for output vector map

DESCRIPTION

v.drape converts 2D vector point or line data into 3D vector format via sampling of an elevation surface. Three sampling algorithms adapted fromv v.sample were incorporated into this module: nearest neighbor, bilinear, and cubic convultion.

NOTES

Please run beforehand

g.region vect=2D_vector

and make sure that the extent of the elevation raster is at least as big as the vector to convert.

Additional vertices can be added to the input 2D vector with v.split.

The module can be used in conjunction with v.out.pov and r.out.pov to export a complete set of vector and raster data for display in POVRAY.

EXAMPLE

Spearfish example:

g.region -p vect=roads align=elevation.10m
v.drape in=roads rast=elevation.10m method=bilinear out=roads3d
v.info roads3d

POVRAY EXAMPLE

#setup the region
g.region vect=roads align=elevation.10m -p
#export the vector data
v.drape in=roads out=roads3d rast=elevation.10m
v.out.pov roads3d out=roads3d.pov
#export the raster data
r.out.pov elevation.10m tga=elevation.tga
r.out.png landcover.30m out=landcover30m.png

# now write a complete povray-script and launch povray

ERROR MESSAGES

If the following error message appears

 WARNING: [demname in mapset] - read request for row -1 is outside region
 ERROR: problem reading raster cell file

it indicates that the vector map is spatially larger than the raster map. To avoid this problem, the vector map needs to be clipped to the raster map extent, for example:

g.region rast=demname
v.in.region clipbox
v.overlay ain=clipbox bin=vectmap out=vectmap_clipped op=and
v.drape vectmap_clipped out=vectdrape rast=demname

Then v.drape should perform the draping.

AUTHOR

Dylan Beaudette, University of California at Davis.
Raster sampling routines borrowed from v.sample.

Last changed: $Date: 2007/07/09 15:15:57 $

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