Optimization based on a map

Hello everybody,

i want to optimize a system, but at some points the System to complex to describe it by formulas. So i made a physical modell an made a parameter sweep analysis to finaly get a map of the part of the System. It looks something like that: It is a discrete map.

Lets say the x axis is the variable a and the y axis is b. Output ist P (power). Now iam searching the maximum power point is this field based on some restrictions to a and b. The real Problem is more complex but it is some like this problem. There are some maps, that needs to be connected.

Do i have to perform a curve fitting or ist there another way to but this problem in a solver??

The problem here would be : max(P) under for eg. -200 < a < 200 and -200 < b < 200

Thank you very much!