How to intersect two rasters

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07-23-2015 10:12 AM
ErikFernandez
New Contributor III

I'm very familiar with using the intersect tool with shapefiles/geodatabases. I have two rasters that I'd like to do the same with. It would be super helpful if someone could point me toward a tool that would do this. Basically, raster 1 has values ranging from 1-10 and raster 2 has values ranging from A-E. I want to be able to create a new raster that tells me for example how many acres have a value of 1 that overlap with value A.  Any suggestions are much appreciated!

Erik

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5 Replies
michaelcollins1
Occasional Contributor III

You could either convert both rasters to shape files and do an intersect, or be a little creative with raster math. Resample the second raster to values in increments of 25 say, and then add the 2 rasters together. The "intersect " would be raster values 26, 51, 76, etc.

DarrenWiens2
MVP Honored Contributor

I believe Tabulate Area will do this for you.

XanderBakker
Esri Esteemed Contributor

If Tabulate Areas doesn't yield the format you require and each combination needs to be on a single record, you can use Combine—Help | ArcGIS for Desktop . This will yield a new raster with the combinations and the attribute table can be used to define the areas (count * pixelsize)

ErikFernandez
New Contributor III

hmmm, the suggestions are close but not exactly the right fit for what I'm trying to do (or it's possible I'm not understanding the suggested tools).

- I tried converting to a shape file and intersecting. Files are too big, never finishes.

- Here's a more thorough explanation of what I'm trying to do. Grid 1 represents all of the counties in Oregon, about 30. Grid two represents a range of values corresponding to how much biomass is stored per acre. I am trying to figure out how much biomass is stored in each county.

- With regard to tabulate area - if you look at the illustration at the link provided above, what I'd like to calculate is for example to look at all of the boxes with 1 as the value in the left box and know what the total values added up in the corresponding 2nd box are that have a 1 in the first box. So the final table would have a field for value, and the first record would be 1 and the the second field would be total and would equal 55. Above real example might be easier to follow.

Again, thank you for the suggestions.

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DarrenWiens2
MVP Honored Contributor

In that case, quite different description than the original btw, you should look into Zonal Statistics, SUM. You may find it easier to create a new raster with absolute values of biomass per pixel, rather than adding biomass per acre, but it's up to you.