topic Re: Kernel Density Empty Geometry in ArcGIS Spatial Analyst Questions

Kernel Density Empty Geometry

CharmaineRice — Wed, 10 Jul 2013 16:19:41 GMT

Hello,

I'm trying to do a Kernel Density on point data but it keeps saying there is a 'general function failure' and that 'the operation was attempted on an empty geometry'. It has worked on previous point data but now I'm at a loss. Does anyone know what might cause this and how to fix it?

Thank you.

Re: Kernel Density Empty Geometry

DerekNelson — Fri, 12 Jul 2013 19:36:20 GMT

Is the point data an imported table or an actual shapefile? I know there tends to be problems bc many people including myself (when I forget) will bring a table in and try to manipulate the data. Many times if you just locate what you are calling the point data in arcmaps table of contents, right-click the file, hover over data and select export data...then designate your output name and use the drop down to shapefile...bring that data in and try again....that's my initial guess or question for you...I have done numerous kernel densities and can help troubleshooting further if it is more complex...lemme know what's up

Re: Kernel Density Empty Geometry

CharmaineRice — Sun, 14 Jul 2013 13:20:48 GMT

Is the point data an imported table or an actual shapefile? I know there tends to be problems bc many people including myself (when I forget) will bring a table in and try to manipulate the data. Many times if you just locate what you are calling the point data in arcmaps table of contents, right-click the file, hover over data and select export data...then designate your output name and use the drop down to shapefile...bring that data in and try again....that's my initial guess or question for you...I have done numerous kernel densities and can help troubleshooting further if it is more complex...lemme know what's up

Hi Derek,

Thank you for your reply. It is a shapefile. I've managed to get it to do a kernel density by using the default cell_size and search radius instead of trying to specify my own. Maybe I was using too large a search radius for the size of the layer, though when I was originally shown how to do it on the same data much larger numbers were used!

Thanks again

Re: Kernel Density Empty Geometry

curtvprice — Thu, 18 Jul 2013 02:25:17 GMT

Maybe I was using too large a search radius for the size of the layer, though when I was originally shown how to do it on the same data much larger numbers were used!

If you are using map coordinates to specify the kernel, double check what the output coordinate system is set to. For example, 3 x 3 degrees is a pretty big kernel!

Re: Kernel Density Empty Geometry

CharmaineRice — Thu, 18 Jul 2013 11:46:10 GMT

If you are using map coordinates to specify the kernel, double check what the output coordinate system is set to. For example, 3 x 3 degrees is a pretty big kernel!

Hi, thanks for the reply,

I'm not sure what you mean but I was doing the Kernel with the point layer selected as the extent and was using metres to specify the search area (hope I'm using the right words, I don't have access to the ArcGIS at the moment). I think I'd made my search area larger than the area of the layer, whereas the first time I was shown the display was used as the extent so could have been a much larger area, so that might have been what was going wrong! I'll have another go!

Re: Kernel Density Empty Geometry

DerekNelson — Wed, 24 Jul 2013 14:14:16 GMT

If you want to leave the default search radius and just make a smaller cell size you can get a smoother (less pixelated) result....depending on your resolution I would try multiple sizes... i.e. .001 (really small)