## NAME

v.kernel

## DESCRIPTION

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.

## NOTES

The mult 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.

With the -o flag (experimental) the command tries to calculate an optimal standard deviation. The value of stddeviation is taken as maximum value. Standard deviation is calculated using ALL points, not just those in the current region.

## LIMITATIONS

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

## SEE ALSO

v.surf.rst

## REFERENCES

Okabe, A., Satoh, T., Sugihara, K. (2009). A kernel density estimation method for networks, its computational method and a GIS-based tool. International Journal of Geographical Information Science, Vol 23(1), pp. 7-32.
DOI: 10.1080/13658810802475491

## AUTHORS

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

Last changed: $Date: 2011-11-08 12:29:50 +0100 (Tue, 08 Nov 2011) $

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