interpulation into look up table

I am trying to convert the Burrill cavitation diagram into Matlab. In this diagram the X axis is between 0.05 and 2.0. The Y axis is between 0.05 and 0.5. In the diagram there are five lines of constant cavitation value (CV). Thus CV1=f1(x,y), CV2=f2(x,y), CV3=f3(x,y), etc.. where CV1=2.5%, CV2=5%, CV3=10%, CV4=20% and CV5=30%
For a value of x and y I would like to interpolate and calculate the CV.
I did not find the iterp2 function usefull for this problem but maybe I am wrong.
Couls someone help please?
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