A method comprising: receiving a first amount of measurement data associated with measurements of a first plurality of measurement sites on a surface of a semiconductor wafer, wherein each of the first plurality of measurement sites includes a single patterned metrology target having a first grating pitch generated by a first patterning step of a multiple patterning process and a multiple patterned metrology target having a second grating pitch generated by the first patterning step and a subsequent patterning step of the multiple patterning process, wherein the single patterned metrology target and the multiple patterned metrology target are disposed adjacent to one another at each measurement site; determining at least one structural parameter value associated with each of the first plurality of measurement sites based on the first amount of measurement data and a combined measurement model being a trained input-output model, wherein a model parameter characterizing the single patterned metrology target and a model parameter characterizing the multiple patterned metrology target are linked in the combined measurement model, and wherein the at least one structural parameter value is indicative of a geometric error induced by the multiple patterning process; storing the at least one structural parameter value in a memory; receiving a second amount of measurement data associated with a second plurality of measurement sites, wherein each of the second plurality of measurement sites includes a single patterned metrology target having a first grating pitch generated by a first patterning step of a multiple patterning process and a multiple patterning metrology target having a second grating pitch generated by the first patterning step and a subsequent patterning step of the multiple patterning process, wherein at least one structural parameter value characterizing the single patterned metrology target and at least one structural parameter value characterizing the multiple patterned metrology target are known at each of the second plurality of measurement sites; determining the input-output measurement model based at least in part on the second amount of measurement data; and training the input-output measurement model based at least in part on the known structural parameter values to obtain the trained input-output model. receiving a first amount of measurement data associated with measurements of a first plurality of measurement sites on a surface of a semiconductor wafer, wherein each of the first plurality of measurement sites includes a single patterned metrology target having a first grating pitch generated by a first patterning step of a multiple patterning process and a multiple patterned metrology target having a second grating pitch generated by the first patterning step and a subsequent patterning step of the multiple patterning process, wherein the single patterned metrology target and the multiple patterned metrology target are disposed adjacent to one another at each measurement site; determining at least one structural parameter value associated with each of the first plurality of measurement sites based on the first amount of measurement data and a combined measurement model being a trained input-output model, wherein a model parameter characterizing the single patterned metrology target and a model parameter characterizing the multiple patterned metrology target are linked in the combined measurement model, and wherein the at least one structural parameter value is indicative of a geometric error induced by the multiple patterning process; storing the at least one structural parameter value in a memory; receiving a second amount of measurement data associated with a second plurality of measurement sites, wherein each of the second plurality of measurement sites includes a single patterned metrology target having a first grating pitch generated by a first patterning step of a multiple patterning process and a multiple patterning metrology target having a second grating pitch generated by the first patterning step and a subsequent patterning step of the multiple patterning process, wherein at least one structural parameter value characterizing the single patterned metrology target and at least one structural parameter value characterizing the multiple patterned metrology target are known at each of the second plurality of measurement sites; determining the input-output measurement model based at least in part on the second amount of measurement data; and training the input-output measurement model based at least in part on the known structural parameter values to obtain the trained input-output model.