A method involving measuring a first metrology target designed for a first range of values of a process parameter; measuring a second metrology target designed for a second range of values of the same process parameter, the second range different than the first range and the second metrology target having a different physical design than the first metrology target; and deriving process window data from a value of the process parameter in the first range determined from the measuring of the first metrology target, and from a value of the process parameter in the second range determined from the measuring of the second metrology target.