v.kernel - Generates a raster density map from vector points map.

       Stefano Menegon, ITC-irst, Trento, Italy
       Radim Blazek (additional kernel density functions and network part)

v.kernel generates a raster density map from vector points data using a moving kernel.  Available  kernel
       density functions are uniform,triangular,epanechnikov,quartic,triweight,gaussian,cosine, default is
       gaussian.

       The  module  can  also  generate a vector density map on a vector network.  Conventional kernel functions
       produce biased estimates by overestimating the densities around network nodes, whereas  the  equal  split
       method of Okabe et al. (2009) produces unbiased density estimates. The equal split method uses the kernel
       function selected with the kernel option and can be enabled with node=split.

       Compute density of points (using vector map of schools from North Carolina sample dataset):
       g.region region=wake_30m
       v.kernel input=schools_wake output=schools_density radius=5000 multiplier=1000000
       r.colors map=schools_density color=bcyr
       School density

       vector, kernel density, point density, heatmap, hotspot

       The module only considers the presence of points, but not (yet) any attribute values.

v.kernel  - Generates a raster density map from vector points map.
       Density is computed using a moving kernel. Optionally generates a vector density map on a vector network.

       The multiplier option is needed to overcome the limitation that the resulting density in case of a vector
       map  output  is  stored as category (integer). The density result stored as category may be multiplied by
       this number.

       For the gaussian kernel, standard deviation for the gaussian function is set to 1/4 of the radius.

       With the -o flag (experimental) the command tries to calculate an optimal radius. The value of radius  is
       taken  as  maximum  value. The radius is calculated based on the gaussian function, using ALL points, not
       just those in the current region.

           •   Okabe, A., Satoh, T., Sugihara, K. (2009). Akerneldensityestimationmethodfornetworks,itscomputationalmethodandaGIS-basedtool.  InternationalJournalofGeographicalInformationScience, Vol 23(1), pp. 7-32.
               DOI: 10.1080/13658810802475491

v.surf.rst

       Overview: Interpolation and Resampling in GRASS GIS

       Available at: v.kernel source code (history)

       Accessed: Friday Apr 04 01:20:20 2025

       Main index | Vector index | Topics index | Keywords index | Graphical index | Full index

       © 2003-2025 GRASS Development Team, GRASS GIS 8.4.1 Reference Manual

GRASS 8.4.1                                                                                     v.kernel(1grass)

v.kernelv.kernel--helpv.kernel  [-oqnm] input=name  [net=name]   [output=name]   [net_output=name]  radius=float  [dsize=float]
       [segmax=float]   [distmax=float]   [multiplier=float]   [node=string]    [kernel=string]    [--overwrite]
       [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:-o
           Try to calculate an optimal radius with given ’radius’ taken as maximum (experimental)

       -q
           Only calculate optimal radius and exit (no map is written)

       -n
           In  network  mode,  normalize values by sum of density multiplied by length of each segment. Integral
           over the output map then gives 1.0 * multiplier

       -m
           In network mode, multiply the result by number of input points

       --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[required]
           Name of input vector map with training points

       net=name
           Name of input network vector map

       output=name
           Name for output raster map

       net_output=name
           Name for output vector density map
           Outputs vector map if network map is given

       radius=float[required]
           Kernel radius in map units

       dsize=float
           Discretization error in map units
           Default: 0.segmax=float
           Maximum length of segment on network
           Default: 100.distmax=float
           Maximum distance from point to network
           Default: 100.multiplier=float
           Multiply the density result by this number
           Default: 1.node=string
           Node method
           Options: none,split
           Default: nonenone: No method applied at nodes with more than 2 arcs
           split: Equal split (Okabe 2009) applied at nodes

       kernel=string
           Kernel function
           Options: uniform,triangular,epanechnikov,quartic,triweight,gaussian,cosine
           Default: gaussian