A method and apparatus to measure a target (e.g., an alignment mark (e.g., on a substrate)) is disclosed. Relative movement between the target and a measurement spot of a measurement system in a “fly-in” direction (e.g., movement of the target towards the measurement spot) is performed so that a first measurement for the target can be made. Thereafter, relative movement between the target and the measurement spot is made in an opposite “fly-in” direction so that a second measurement for the target can be made. By combining (e.g., averaging) these two measurements, an error is cancelled out, and higher accuracy in the measurement may be achieved.