topic Re: Con statement with raster calculator in ArcGIS Spatial Analyst Questions

Con statement with raster calculator

TahirTamba1 — Fri, 27 Feb 2015 20:56:10 GMT

Hi all,

I would like to know if there is a way to perform a conditional raster calculation between two layers A and B.

I would like to have the following conditions:

If (inRastA <= 43) (condition 1) and (inRastB> = 42) (condition2) and (inRastA+inRastB <= 85) (condition3), then the result is (ouRast = 86), otherwise (inRastA+inRastB).

How can I write this statement within the Raster Calculator?

Below the same example written in Excel

=IF(And(A1<=43; B1>=42; O1<=85);86;O1+B1)

Regards!

Re: Con statement with raster calculator

DarrenWiens2 — Fri, 27 Feb 2015 21:33:08 GMT

You have obviously found the Con tool. Save us some time and post what you have so far.

edit: the short answer to your first question is, yes, it is possible to do this using Con.

Re: Con statement with raster calculator

EtiOst — Fri, 27 Feb 2015 22:35:38 GMT

Try this:

Con(("inRastA" <= 43") & ("inRastB" >= 42) & ("inRastA" + "inRastB") <=85, "ouRast" == 86, "inRastA" + "inRastB")

Hope it works

Re: Con statement with raster calculator

TahirTamba1 — Mon, 02 Mar 2015 06:19:16 GMT

Hi Darren,

To be more explicit, we generated two interpolation grids using the kriging method for contaminated soils from two groups among ala contaminated soil classification scheme adopted by the Ministry of Environment of Quebec. The soils of the BC class (contaminated) represents the interpolated surface grid for this class. The second class represents C + and C + RESC soil very contaminated.
After interpolation of the two categories that represent the same sampling point, we wanted to overlay the two grids to get a final grid that gives us an overall picture of the contamination.
For this, we performed a classification of pixel values, according to three classes, based on the class limits determined by the statistics obtained for the soils of the BC class and C + and C + RESC. By performing the overlaid of two raster layers, we would like to have the pixel values of the BC layers and C + and C + RESC that fulfill the criteria we determined. The result of the Con is depected by the last image.

See attachment below.

Regards

Re: Con statement with raster calculator

TahirTamba1 — Mon, 02 Mar 2015 06:32:49 GMT

Hi Eti,

Thank for your answer. I've tried the Con argument you pointed me out based on the criterion we determined to overlay the two raster grid we generaeted. Curiously, I get the same result as a simple addition operation between the two layers. View the files attached to the answer of Darren post.

I'm wondering if our reasoning does make sense?

Thank again for your help

Re: Con statement with raster calculator

KishorGhatage — Mon, 02 Mar 2015 07:19:39 GMT

Could you please try this:

Con(("inRastA" <= 43) & ("inRastB" >= 42) &(("inRastA" + "inRastB") <=85),86, ( "inRastA" + "inRastB"))

Re: Con statement with raster calculator

DanPatterson_Retired — Mon, 02 Mar 2015 10:11:55 GMT

=IF(And(A1<=43; B1>=42; O1<=85);86;O1+B1)
If (inRastA <= 43) (condition 1) and (inRastB> = 42) (condition2) and (inRastA+inRastB <= 85) (condition3), then the result is (ouRast = 86), otherwise (inRastA+inRastB).

There are 2 conditions in the first

There are 3 conditions in the second

Can you confirm the logic

Using the IF statement as the one that worked:

True = if A1<=43 AND B1 >42 and O1 (A1+B1 <=85) then 86

False = else A1 + B1

So the first checks should be

con 1 , con 2 , True_1&2, False_2, False_1

(A1+B1 < = 85), [ (A1<=43 and B1>=42), True, False], False)

(A1+B1 < = 85), [ (A1<=43 and B1>=42), 86, A1+B1], A1+B1)

(test 1,

True1 [ (test 2,

(True 1 and True 2), 86

True 1, False 2) A1 + B1

False 1 A1 + B1

Re: Con statement with raster calculator

TahirTamba1 — Mon, 02 Mar 2015 14:35:07 GMT

Hi Dan,

Sorry to mislead you. The first condition is what my colleague has done in Excel using the non kriged data. She just wanted to provide the syntax of a conditional request to Excel as an example. I was afraid that it induces the readers into error, but she insisted ...

But in reality, it is probably the second case we would like to evaluate the three conditions from two rasters provided, in my previous post

Regards.

Re: Con statement with raster calculator

TahirTamba1 — Mon, 02 Mar 2015 15:02:07 GMT

Hi Kishore,

Thank for the example you provide. I'll will try it soon and I'll get back to you soon...

ReRegards!

Tahir Tamba

6632, Avenue de Gaspé

Montréal, H2S 2Y2

Re: Con statement with raster calculator

EtiOst — Mon, 02 Mar 2015 20:35:52 GMT

Hi, if I understand well, you are trying to adjust the superposition raster pixel values in order to show up the contamination for the cases you have contamination in one of two grids but when you do the sum of their contamination limit intervals values, it disappears. I guess, if you fix 85 (42+43) as a limit for a contamination class of the superposition grid, and you have values greater than 42 (image 2) and less than 43 (image 1), your superposition grid (image 3) will not show the contamination represented by the values greater than 42 of image 2 and the values less than 43 of image 1 because their sum is less than 85 (for example 45+30=75). I think your conditions are good, I don’t know why it doesn’t work.

Re: Con statement with raster calculator

TahirTamba1 — Thu, 19 Mar 2015 14:20:01 GMT

Hi Kishore,

Sorry not being able to give you a feedback regarding Con statement we were trying to achieve for better overlaying the two input raster grids I sent in my previous posts.

My boss put me in a rush for an urgent project that we have to deliver this week. This is why I have not had a chance to get back to you about my request.

I finally tested your "Con" statement and the result seems to match what we expected.
Thank you Kishore for your help.

Thank also all of you for pointing me out the syntax for Con statement. I really appreciated!

Best regards.

Re: Con statement with raster calculator

TahirTamba1 — Thu, 19 Mar 2015 14:39:36 GMT

Dan,

What we want to achieve is to overlay two raster grids with using 3 conditions mentioned in the second stament you pointed out. Looking to your first check statement logic, I think this logic summerize the Con statement that Kishore suggest.

But can't figure out how to achieve this using Spatial Analyst Con staement.

Regards.