topic Rasters with different cell sizes - problem in Geoprocessing Questions

Rasters with different cell sizes - problem

ValentinSarac — Tue, 04 Dec 2012 11:12:28 GMT

Hi,

Please help me with the following problem in ArcMap 10.1

I had 2 rasters each with cell of size 30 (one which contains information about the type of construction and one with the county it belongs to). I combined the two rasters in one which has links to the other 2. Now I have to calculate how many of these cells of a specific type of construction exist in a bigger cell (size = 1000). So I created a third raster with size = 1000.
I tried to combine the third raster with the combination of the first two but what I obtain is a raster with only one entry for each of the bigger raster cells. What I would need is a raster file which has an entry for each small raster cell of a specific type of construction in each county and in each big cell. Example:
Raster A: cell size = 30, types of construction: "house", "apartment","nothing", 30000 cells in the whole country
Raster B: cell size = 30, 40 counties in the country, 30000 cells divided by counties
Raster C: cell size = 1000

Result raster: cell size = 30?, type of construction="house", county X, Raster C cell index, how many cells of the type house are in this "Raster C cell index" and in this COUNTY

If you could please give me some indications (and as many details as possible:)) on how to solve this problem using ArcGIS Desktop I would really appreciate it.

Thank you!

Re: Rasters with different cell sizes - problem

markdenil — Wed, 05 Dec 2012 12:43:45 GMT

You likely want to convert your data rasters to polygons (with NO_SIMPLIFY),
then create a fishnet with 1000 (whatever the unit) cells,
and union them all.

Now you can use the FID of the 1000 fishnet to calculate the proportion of
the area of each of the other data set features that fall inside that cell.

for example in the fishnet cell FID = 1:
rasterA 35%
rasterB 40%

If you pack that data into one field,
say by multplying the rasterA value by 1000 (so the 35 in the example is 35000)
and adding it to the rasterB value (40 in the example)
so you get a cell value of 35040 (again, in the example),
you can use that new packed-value field as the value field in a polygonToRaster operation.

(of course, that trick assumes you have rounded your percentages to integers)

Re: Rasters with different cell sizes - problem

ValentinSarac — Wed, 05 Dec 2012 18:48:58 GMT

Hi and thanks for your post. Actually, I do not want to convert to polygon. I converted the polygons to rasters and all the processing has to be done on rasters now. Any other ideas?