I'm starting to use the Grass module on QGIS, and I want to do a heatmap, so, I'm creating a new surface using the kernel function. But, GRASS come with 7 types of kernel functions, how do I know which one to choose?



There are two questions to answer in deciding a kernel shape. First. How large an area will have the effect from an incidents. Second. How much of the effect will remain at original location and how much will be dispersed throughout the bandwidth interval. For example if you think the effect of accident will decrease in linear pattern from an original location, then Triangular Kernel would be a good option. Otherwise if the accident will have the same effect throughout a specified radius, the Uniform kernel would be a good option. So understanding the two questions above for a case will give a better decision in choosing a kernel shape and related parameters. Refer to this link for more...


The v.kernel manual offers a link to a Wikipedia page explaining the various kernels. In essence, it depends on your problem but to start with the default "Gaussian" may be just fine.

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    If we look on the Asdar book on the chapter 7, it demonstrate is almost the same with different functions. What make the difference is the band width. So, for the best result, we need to find the optimal band width. – Ariel Jul 9 '13 at 2:34

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