ARC DISTANCE MODE (G90.1 AND G91.1)
G90.1 – Absolute distance mode for I and K offsets. When G90.1 is in effect, I and K both must be specified with G02/G03 for the XZ plane or it is an error.
G91.1 – Incremental distance mode for I and K offsets. G91.1 returns I and K to their default behavior.