A position determining method for continuously determining the spatial position of an auxiliary measuring instrument having at least one auxiliary point marking (22, 32, 32a, 32b), comprising • continuously detecting camera images of the at least one auxiliary point marking (22, 32, 32a, 32b) by means of a camera (12, 61) with an area sensor (30, 50) having a multiplicity of pixels (38a-d, 42), • continuously carrying out read-out passes in which at least some of the pixels (38a-d, 42) are read out with regard to a respective current exposure value, • continuously determining at least one image position for the at least one imaged auxiliary point marking (22, 32, 32a, 32b) in the respective current camera image depending on exposure values obtained in the context of the respective current read-out pass, and • continuously deriving the respective current spatial position of the auxiliary measuring instrument on the basis of the at least one current image position, wherein the at least one image position is determined by the following steps • filtering pixels (38a-d, 42) for which the exposure value obtained during read-out fulfills a threshold value criterion, in particular lies above a threshold value, • joining together filtered pixels (38a-d, 42) that form line regions that are coherent in a line (37a-d, 41) of the area sensor (30, 50) in each case to form line segments (39a-d, 51a), • ascertaining respective centroid portions for each of the line segments (39a-d, 51a), • grouping the line segments (39a-d, 51a) in such a way that such line segments (39a-d, 51a) which belong to the at least one imaged auxiliary point markings (22, 32, 32a, 32b) are in each case assigned to one another, and • deriving the at least one image position of the at least one auxiliary point marking (22, 32, 32a, 32b) with the aid of the corresponding respective centroid portions of the line segments (39a-d, 51a) which are in each case assigned to one another wherein • in the context of the read-out passes the area sensor (30, 50) is read out pixel (38a-d, 42) by pixel (38a-d, 42) and line (37a-d, 41) by line (37a-d, 41) with a predefined pixel read-out rate, and • at the latest directly after completion of the read-out of respectively one line (37a-d, 41) already for this one line (37a-d, 41) the steps of filtering, joining together and ascertaining respective centroid portions, which steps are carried out in the context of determining the at least one image position, are started and carried out. • continuously detecting camera images of the at least one auxiliary point marking (22, 32, 32a, 32b) by means of a camera (12, 61) with an area sensor (30, 50) having a multiplicity of pixels (38a-d, 42), • continuously carrying out read-out passes in which at least some of the pixels (38a-d, 42) are read out with regard to a respective current exposure value, • continuously determining at least one image position for the at least one imaged auxiliary point marking (22, 32, 32a, 32b) in the respective current camera image depending on exposure values obtained in the context of the respective current read-out pass, and • continuously deriving the respective current spatial position of the auxiliary measuring instrument on the basis of the at least one current image position, wherein the at least one image position is determined by the following steps • filtering pixels (38a-d, 42) for which the exposure value obtained during read-out fulfills a threshold value criterion, in particular lies above a threshold value, • joining together filtered pixels (38a-d, 42) that form line regions that are coherent in a line (37a-d, 41) of the area sensor (30, 50) in each case to form line segments (39a-d, 51a), • ascertaining respective centroid portions for each of the line segments (39a-d, 51a), • grouping the line segments (39a-d, 51a) in such a way that such line segments (39a-d, 51a) which belong to the at least one imaged auxiliary point markings (22, 32, 32a, 32b) are in each case assigned to one another, and • deriving the at least one image position of the at least one auxiliary point marking (22, 32, 32a, 32b) with the aid of the corresponding respective centroid portions of the line segments (39a-d, 51a) which are in each case assigned to one another wherein • in the context of the read-out passes the area sensor (30, 50) is read out pixel (38a-d, 42) by pixel (38a-d, 42) and line (37a-d, 41) by line (37a-d, 41) with a predefined pixel read-out rate, and • at the latest directly after completion of the read-out of respectively one line (37a-d, 41) already for this one line (37a-d, 41) the steps of filtering, joining together and ascertaining respective centroid portions, which steps are carried out in the context of determining the at least one image position, are started and carried out.