topic arithmetic operation of point fetures over raster cell area in Spatial Data Science Questions

arithmetic operation of point fetures over raster cell area

BrettBonner — Sun, 16 Aug 2015 17:04:36 GMT

I have a raster file with a human population count for each raster cell.

I have another layer with x,y,z vector point features.

I want to sum the z values of all point features that lie within each raster cell area, and divide that sum by the human population value in the raster cell. Ultimately I want to map z-per-capita.

How should I approach this exercise and what tools should I use within my evaluation copy of ArcMap 10.3? I am new to GIS and the learning curve for ArcGIS is immense, so I hope my question makes sense.

If there is a tutorial guide or video with a roughly similar operation, please let me know.

Re: arithmetic operation of point fetures over raster cell area

XanderBakker — Sat, 22 Aug 2015 22:32:15 GMT

I'm not so sure about the "makes sense" part, but strictly speaking you could convert your x,y,z points to raster: Point to Raster—Help | ArcGIS for Desktop , using the Z as value field and SUM as cell assignment. This will yield a raster with the Z values summed per cell (make sure you set the geoprocessing environment to match the extent, cellsize and snap raster to the other population raster you already have.

The next step would be to use the divide tool from Spatial Analyst to divide the population raster by the summed Z raster. If the results makes sense, depends on the data you have. In case a cell in either raster has no data, the result will be no data.

Re: arithmetic operation of point fetures over raster cell area

BrettBonner — Fri, 28 Aug 2015 03:54:24 GMT

This is what I ended up performing:

I created a fishnet to the extents and according to the cell size of the raster, and converted the fishnet to polygons.

Then I converted the raster to point feature centroids.

Next, I used a spatial join to join the point feature centroids and also the sum of point features within the polygons created from the fishnet.

Finally, using the attribute table I created a new field and simply divided by the once-raster values column by the point feature sum column. Voila I have performed arithmetic using raster z-values.