The invention relates to a method and a device (1) for determining the leading edges (S1, S2) of two overlapping image captures of a surface (OF), comprising at least one camera (2) having a matrix-type sensor (6), having n lines (7), a position and location measuring system (3), an evaluation unit (4) and a storage means (5), wherein an elevation model (H) of the surface (OF) and a projection model (P) of the camera (2) are stored in the storage means (5), which the evaluation unit (4) can access, wherein the camera position (P1, P2) in the first and second image capture is determined by means of the position and location measuring system (3), wherein a horizontal mid-point (M) between the two camera positions (P1, P2) is determined and a projection of the mid-point (M) onto the surface (OF) is carried out, wherein a back projection onto the sensor (6) is carried out in the first and second camera position (P1, P2) by means of the projection model (P) for the point (MO) determined in the above-mentioned manner and a respective pixel is determined, wherein the respective line of the sensor (6) is determined, four solid angles (RW1-4) of the respective first and last pixel (Pix1-4) of the lines (7.Z1 M0, 7.Z2M0) are determined and their leading points (SP1-SP4) are determined with the elevation model (H), mid-points (M1, M2) are determined between the leading points and projected back into the sensors in the first and second position, associated lines are determined, wherein the smallest determined line (7.MIN1) is selected as the leading edge (S1) for the first camera position (P1) and the largest determined line (7.MAX2) is selected as the leading edge (S2) for the second camera position (P2).