NAME
v.surf.nnbathy - Interpolates a raster map using the nnbathy natural neighbor interpolation program.
KEYWORDS
vector,
surface,
interpolation,
natural,
neighbor
SYNOPSIS
v.surf.nnbathy
v.surf.nnbathy --help
v.surf.nnbathy [input=name] [layer=string] [file=name] output=name [column=name] [where=sql_query] [algorithm=string] [--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags:
- --overwrite
- Allow output files to overwrite existing files
- --help
- Print usage summary
- --verbose
- Verbose module output
- --quiet
- Quiet module output
- --ui
- Force launching GUI dialog
Parameters:
- input=name
- Name of input vector map
- Name of input vector points map
- layer=string
- Layer number
- If set to 0, z coordinates are used. (3D vector only)
- Default: 1
- file=name
- Containing x,y,z data as three space separated columns
- output=name [required]
- Name of output raster map
- column=name
- Name of the attribute column with values to be used for approximation (if layer>0)
- where=sql_query
- WHERE conditions of SQL statement without 'where' keyword
- Example: income < 1000 and population >= 10000
- algorithm=string
- Settings
- Options: l, nn, ns
- Default: nn
- l: Linear
- nn: Sibson natural neighbor
- ns: Non-Sibsonian natural neighbor
v.surf.nnbathy is an interface between the
external
nnbathy utility and
GRASS.
nnbathy is a surface interpolation program provided with
nn - a natural neighbor
interpolation library, written by Pavel Sakov.
v.surf.nnbathy provides 3 interpolation algorithms. According to
nn library documentation these are: Delaunay interpolation
(alg=l), Watson's algortithm for Sibson natural neighbor
interpolation (alg=nn) and Belikov and Semenov's algorithm for
non-Sibsonian natural neighbor interpolation (alg=ns). For performing
the underlaying Delaunay triangulation in all cases nnbathy uses
triangle software by
Jonathan Richard Shewchuk.
The output raster map is a continous surface interpolated from the
input or file data.
nnbathy, if built with '-DNN_SERIAL' (default as of nn 1.85), is
able to create a grid of virtually any size. It interpolates and writes one
output point at a time only. This eliminates the necessity to hold the whole
output array in memory. However, even then all the input points are still
held in the memory.
- Requires GRASS 7 and nnbathy 1.76 or greater.
- Build nnbathy according to instructions provided with its source
code and put it somewhere in your $PATH.
- The output raster map extent and resolution match the region settings at
which the script was started.
- The output raster map non-NULL area is limited to the convex hull
encompassing all the non-NULL input cells.
- The output is double precision floating point raster map (DCELL).
- Natural neighbor is a an exact interpolation algorithm, so all
non-NULL input points have their value exactly preserved in the output.
- There is circa 0.2 KB memory overhead per each input cell.
However, the output grid can be of any size, if nnbathy is
built with -DNN_SERIAL switch.
- v.surf.nnbathy creates 4 temporary files: ASCII x,y,z lists of
the input points and output cells, and the output list converted into GRASS ASCII
format. Then it makes a GRASS raster map from the latter - and only then it
removes the 3 temp files, when the script terminates. Thus, at the script
run time several times more disk space might be required, than the final
GRASS raster map would actually occupy.
g.region raster=elevationelev_lid792_randpts@PERMANENT -p
v.surf.nnbathy input=elevation_lid792_randpts@PERMANENT output=raster_map column=value
d.rast map=raster_map
r.surf.nnbathy
Adam Laza, OSGeoREL, Czech Technical University in Prague (mentor: Martin Landa)
Corrected by Roberto Marzocchi,
roberto.marzocchi@gter.it
Based on v.surf.nnbathy from GRASS 6 by:
Hamish Bowman, Otago University, New Zealand
Based on r.surf.nnbathy by Maciej Sieczka
SOURCE CODE
Available at:
v.surf.nnbathy source code
(history)
Latest change: Thursday Nov 09 15:37:21 2023 in commit: 1767c5f65fed3c5293f41668925558ea39c6e4ac
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GRASS Development Team,
GRASS GIS 8.4.1dev Reference Manual