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I have a problem when using the con() argument.

What I want to do is to remap all raster of a raster file ("Red_SL") cells with values larger than 40 to the new value 5. All other values should be replaced by another raster file called "remap2". "remap" 2 contains only 4 definite values (1,2,3,4), and "Red SL" has continuous values between 0 and 90.

My syntax is the following:

import arcpy
from arcpy.sa import *

arcpy.env.overwriteOutput = True
arcpy.env.workspace = r"D:\\Projekt\\Testprojekt\\Daten\\Ergebnisse\\"
arcpy.CheckOutExtension("Spatial")
remaped2 = "remaped2.img"
slope = "Red_SL"

CF= Con((slope < 40), 5, remaped2)
CF.save("Red_SL_Neigung_int.tif")
arcpy.CheckInExtension("Spatial")

now the problem is: I do not get an error message but the produced file is nonsense! Python is somehow not able to recognize the slope value in: CF= Con((slope < 40), 5, total) This means it doesent matter what value I give python (here I set it to 40, but I will get the exact same result if I give values of 1 or 3000), the result will always be the a new file which is exactly the same as "remaped2". Python therefore thinks all values are below 40 (or whatever number I give), which is not true.

The exact opposite happens if I change the "<" to ">" (CF= Con((slope > 40), 5, total)). Now I will get i new file, which has only 5 in every raster cell. Here again the value whch I type in (instead of 40) does not matter, any value between 1 and 3000 will produce the exact same result. I double checked, but the file "Red_SL" has all values between 0 and 90, therfore the result I get from python is nonsense.

I already tried (without sucess): -Change "Red_SL" from floating to integer -try differend formats (tif, grid, img) for "Red_SL" - replace comma in floating raster with points (german vs. englisch delimiters)

Can anyone see what is wrong with my use of the Con arguement?

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  • As you have put an r in front of the string for the workspace you do not need to use \\ use a single \.
    – Hornbydd
    Jul 30, 2014 at 13:40
  • Thank you. I removed the doubleslashes but it has no effect on the the problem. Anyway, good to know!
    – Christophmang
    Jul 30, 2014 at 13:42
  • Yes you are right. I am sorry but this was just o fault of myself which happened wehn I copied the syntax into the forum (I have tried so many ways that I had to rechange some stuff). However, I changed it in the posted syntax as well as on my computer but still the same results
    – Christophmang
    Jul 30, 2014 at 13:50

1 Answer 1

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3

You need to create raster objects when working with many of the spatial analyst tools, including Con (Spatial Analyst). Try the following changes:

import arcpy
from arcpy.sa import *

arcpy.env.overwriteOutput = True
arcpy.env.workspace = r"D:\Projekt\Testprojekt\Daten\Ergebnisse"
arcpy.CheckOutExtension("Spatial")
remaped2 = Raster("remaped2.img")
slope = Raster("Red_SL")

CF= Con((slope < 40), 5, remaped2)
CF.save("Red_SL_Neigung_int.tif")
arcpy.CheckInExtension("Spatial")
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2
  • Thats the solution! Thanks a lot for your help everything works fine now!!
    – Christophmang
    Jul 30, 2014 at 13:58
  • @Christophmang if this is a solution for you, you should tick it as correct.
    – Hornbydd
    Jul 30, 2014 at 15:39

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