Is any of these functions helpful for you?

http://gwyddion.net/documentation/user-guide-en/leveling-and-background.html

Dear Abinash,

You have to set up all Gwyddion parameters at the same values and mentioned that in your work,

Regards,

Akram

I am agree with Jurgen, see also http://gwyddion.net/documentation/user-guide-en/statistical-analysis.html and https://scholarsmine.mst.edu/cgi/viewcontent.cgi?article=8267&context=masters_theses

Jürgen Weippert thank you for the recommendation. But I need to fix a constant height for all of my AFM data file

Hi Abinash (Abinash Adhikari )

If you are looking for roughness assessment from AFM, please check the answers in this thread: https://www.researchgate.net/post/how_to_calculate_surface_roughness_factor_from_AFM_analysis

Thank you