Spatial accuracy correction method and apparatus

A spatial accuracy correction apparatus comprising:

• a positioning machine that displaces a displacer to a predetermined set of spatial coordinates, the positioning machine comprising a retroreflector mounted to the displacer, the positioning mechanism being configured to measure a measurable value of the spatial coordinates of the retroreflector;
• a laser interferometer having a reference point and configured to measure a measurable length value that is a distance from the reference point to the retroreflector;
• and
• a controller operably connected to the positioning machine and the laser interferometer, the controller comprising a processor and a memory that stores an instruction, wherein the processor, when executing the instruction stored in the memory, performs operations comprising:
• displacing the retroreflector to a plurality of measurement points in order,
• acquiring the measured length value and measured value measured at each of the measurement points,
• conducting at least one or more repeated measurement for at least one of the plurality of measurement points being measured after conducting measurement of the measured length value and the measured value for each of the plurality of measurement points, and
• when an error by the repeated measurement of the measured length value with respect to the measurement point that has undergone the repeated measurement is equal to or greater than a predetermined threshold value, again measuring the plurality of measurement points.