1. A method of determining a parameter of a target, comprising providing a plurality of reference targets having a plurality of different known one or more parameters values and a plurality of production targets, each reference target having an imaging structure and a scatterometry structure; at a plurality of different operating parameters of the metrology tool, obtaining an image of the imaging structure for each reference target with an imaging channel of a metrology tool, wherein each imaging structure for each reference target includes unresolved features; at the plurality of different operating parameters of the metrology tool, obtaining a scatterometry signal from the scatterometry structure for each reference target with a scatterometry channel of the metrology tool; determining at least one parameter for the plurality of reference targets based on both the image and the scatterometry signal for each of the plurality of reference targets; and determining a recipe by selecting a subset of the different operating parameters of the metrology tool based on which of the determined at least one parameter for the plurality of reference targets most closely matches the known different one or more parameters of the reference targets; and after the recipe is determined, repeating the operations for obtaining an image and/or scatterometry signal and determining at least one parameter for the plurality of production targets, wherein each imaging structure for each production target includes unresolved features.