topic Re: Getting Mean statistic from kriged surface in ArcGIS Spatial Analyst Questions

Getting Mean statistic from kriged surface

Anonymous User — Tue, 28 Aug 2012 02:00:37 GMT

Original User: Vadrosaul

Currently on ArcInfo 10, using ArcMap. I have a point shapefile with 1984 records of parishes/estates, and wish to get mean population data into the 1984 records by using 'Zonal Statistics as Table' and pointing it to a kriged surface generated from another point shapefile that's comprised of markettown populations.

The Zonal Statistics table is generated, but is lacking around 150 records, most of which I have confirmed are points that are covered by the kriged raster surface. Why would some records not get included in the statistics table?

I use a uniqueID for each parish & estate. The attached images show the inputs used in the Kriging and the Zonal Statistics as Table.

Re: Getting Mean statistic from kriged surface

EricRice — Tue, 28 Aug 2012 15:26:23 GMT

The points are converted to raster internally. You probably have a resolution large enough that two or more points are in a single cell. Since the cell can only be 1 value it takes the point with the highest feature ID. This is discussed in the tools documentation under "Usage".

You should note that since you are using points, not polygons, your really just sampling the input value raster. It's not actually calculating a mean value. You should see that Min, Max, and Mean are all the same value. If you were to buffer the points and use those polygons as the zone features, then you would get a real mean calculation.

Best,
Eric

Re: Getting Mean statistic from kriged surface

Anonymous User — Thu, 30 Aug 2012 22:14:25 GMT

Original User: curtvprice

You may want to try the tool Extract Values To Points. But it does look like you may instead want to get polygons (instead of points) for your parishes and use them as zones for Zonal Statistics.