I am summarizing some population data using a 1km raster overlay. I converted population data, polygon layer, into a 25-meter raster that contains the value for population/m^2. That value is then multiplied by 625 m^2 (the area of each cell), then I figured that I could do a zonal summary using my 1km raster layer (which is snapped nicely to the 25-meter raster layer), but now I am stuck. If I could just add up the values of each 25-meter cell that occurs in a 1-km cell then I would only need to multiply by 625 to get the approximate total population in that cell… I could use a majority resample but this should give a better estimate.
I got some great advice on coding a solution, but I'd like to figure it out along this line of thinking if possible.
Best Answer
If you want to stay completely in raster it would be nice if Resample had a Sum method, but as long as you have Spatial Analyst available Zonal Statistics should be able to solve your problem.
If using another raster for your zones, each zone (which will be each cell in this case) needs a unique value. Are all 1km cell values the same? If so, you'll need to alter the raster and/or add a Raster Attribute table. Alternatively, rather than use a raster for zone input, you can just use your fishnet (assuming it's polygons). See the Zonal Statistics help link above - there are several considerations for the raster or vector used for zone definition (cell size, snap, number of bands, presence of a Raster Attribute table, etc.).
The resulting output should be a 1km cell raster with each cell the sum of your 25m raster cell values. You can then run this output raster through Raster Calculator for your [625 x each cell] operation for a final summary raster.
If you want to work in tables, there is also the Zonal Statistics as Table tool which creates a table rather than a raster output. Note that both it and creating a Raster Attribute table already summarize identical cells as single records in the table with a frequency count, not individual cell records. If you want a table with each cell as a record (assuming they aren't already all unique values) you can refer to How to get values of each cell in raster attribute table?