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Question 
How can I compare two scenario outputs by creating a difference map between two dfsu files?

Answer
There are different options to achieve this:

#01. Using the MIKE Zero Data Manager tool: Edit (menu) --> Calculator
In here you can subtract the item values in one file from an item in another file. When you want to find the difference between two files you typically use the expression File1-File2. 
Using Calculation mode you have the option to force the calculations to use interpolated values from the added files instead of discrete values as per default.

Special notice must be given to the way the Data Manager calculates the difference between two files.

If the two files do not have the same mesh, and/or vertical resolution in case of 3D files, then uncheck the "Discrete values" checkbox and the values in File2 will be interpolated to the element positions of File1. The interpolation is carried out using the values from the adjacent elements.
Note: In case of un-linear gradients in the horizontal or vertical direction this may lead to considerably different values in the interpolated file compared to the original file, - even if the dislocation of the element center is minimal. Hence the subtraction of the two files may give unexpected results.
 

#02. Using DHI.MikeCore.Util functionality
DHI.MikeCore.Util contains the ability to subtract two dfsu files from each other. A compiled version of the tool can be downloaded from: https://github.com/DHI/MIKECore-Examples/releases

Run the .exe without arguments, and it will print usages to the console.

The source code can also be downloaded if you want to modify or improve tool functionality.


#03. Using the ‘Compare’ option in MIKE+
After loading two result files in the ‘Results’ tab on the left panel in MIKE+, you can create a new result file containing differences between loaded files. Select the first result file to compare and then click the ‘Compare…’ button, and you will be asked to select another result file to compare with. The newly created file will contain the differences for all common result items available in the two input files.

This tool is designed to compare two scenarios of the same model setup, and it is expected that the two input .dfsu files have the same mesh structure, and the same time step interval.

Note: This tool supports other result file formats supported in MIKE+, including e.g. .dfs2 result files.


FURTHER INFORMATION & USEFUL LINKS
Calculator in Data Manager (Online help)
Description of DHI.MikeCore.Util
Result Comparison in MIKE+ (Online help)

Related Products: MIKE 21/3, MIKE+
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