irradiating a reticle or a mask containing a design pattern, each occurrence of irradiation representing a value of a member of a set of lithographic operating variables, wherein the reticle or mask imparts the occurrences of irradiation design pattern information corresponding to each of the values of the member of the set, wherein the lithographic operating variables are focus, dose, and/or overlay, wherein the lithographic operating variables are modulated such that only one of the lithographic operating variables is modulated and that dies are compared at a same modulation condition, wherein a control modulation with a nominal condition is included at a center of the design pattern, wherein the control modulation is used in an entirety of at least one row of the dies in a first direction, wherein the one of the lithographic operating variables is modulated on either side of the row with the nominal condition and within a process window, and wherein the lithographic operating variables modulated on either side of the nominal condition are disposed on opposite sides of the control modulation in a second direction of the design pattern perpendicular to the first direction such that a different one of the lithographic operating variables is used on the opposite sides of the control modulation whereby the one of the lithographic operating variables that is modulated is only on one of the opposite sides of the control modulation;

patterning a patterning recording material of a wafer during the irradiating, wherein the irradiating carries the design pattern information imparted by the reticle or mask;

recording in the pattern recording material a spatial pattern corresponding to the design pattern information imparted by the reticle or mask for each of the values of the member of the set, each spatial pattern being recorded at a different region of the pattern recording material;

determining from the recorded spatial patterns a presence of a pattern anomaly associated with the pattern, patterning process, or patterning apparatus; and

determining from the recorded spatial patterns a change in the process window over time due to a condition of a process tool that fabricated the wafer.