A method for detecting deformations and errors and/or for generating position data of an instrument (1) with at least one first section (2) with at least one first sensor (4) and at least one second section (3) with at least one second sensor (5), wherein the method encompasses metrologically determining the position of the first and second sensor (4, 5). The method encompasses mathematically determining the position of the second sensor (5) with regard to the first section (2), preferably in at least two ways. Further, an apparatus for executing the method is specified.