Kernel Density Estimation Crimestat

I calculated a series of Kernel Density Estimations in CrimeStat (because more parameters can be set than in the built-in tool in ArcGIS) and then imported the results into ArcMap. I wanted to combine all the Kernel Density Estimations to get an overall result by using the Raster Calculator so I can assign different weights to each Kernel Density Estimation. But the Raster Calculator only accepts actual rasters, while crimestat can only output vector grids. Is one of these solutions possible:

1. convert the vector grids to raster grids without loosing the original values? (when I use Polygon or Feature to Raster the grid looks totally different and I don't know why, it should look exactly the same only with a different format)

2. use a different tool instead of the Raster Calculator that accepts vector grids? I thought of a Spatial Join, but I need to weigh every layer differently and also the Spatial Join takes forever because of all the little grid cells.

• have you researched SPACE? it is a free crime analysis extension for ArcGIS 10 arcgis.com/home/item.html?id=cd0bc6c443b64eaab21d944598a00337 – Mapperz Sep 21 '15 at 16:01
• I am not sure I can get deep enough into the statistics to explain it, but you should not add together the results of different kernel density estimations, even if using the same bandwidth. Technically, it could work, but there are many ways the analysis can go wrong if you are not controlling for bandwidth, underlying population, sampling, etc. Instead, you should create a new weighted sample population and use the entire population to build a new kernel density estimate. – blord-castillo Sep 21 '15 at 16:05
• blord-castillo makes a great point, and this can be implemented in CrimeStat. Also as an FYI CrimeStat can export rasters, such as ASC or GRD files. – Andy W Sep 21 '15 at 20:08
• thank you! all of that is very useful information, I'm relatively new to crime analysis, so I really appreciate your answers! however I'm not sure how to export rasters from crimestat, I only have four options which are SHP, BNA, MIF and KML. But I won't do the KDE anyway now that I know I'm not meant to combine the results! Thanks for the hint on the free crime analysis extension! – danielaandrea Sep 21 '15 at 20:15
• I believe that the crimestats KDE results are stored as a point array (equally spaced points representing cell centers). All you have to do is know the grid spacing of the points and you can use a point to raster tool in arcgis to convert the point (vector) array to a raster. – Jeffrey Evans Sep 21 '15 at 21:31