A substrate including a target structure formed in at least two layers. The target structure includes a first region having periodically repeating features in each of the layers measureable using optical metrology; and a second region having repetitions of one or more product features in each of the layers, the repetitions being sufficient for stochastic analysis to determine at least one local variation metric. The method also includes determining a correction for control of a lithographic process based on measurement of such a target structure.