Method for updating an image portion of a camera image , depicted on a monitor for the purposes of replacing an external mirror of a vehicle , during the cornering of a train consisting of the vehicle and a trailer , - the image portion being updated in accordance with a most probable position (PK) of at least one prominent point (KP1) on the trailer , characterized in that the following is carried out to determine the most probable position (PK): - a three-dimensional model with the object position (P3, P5, P8) of at least one object from the camera image (104, KB) is determined by means of a surround reconstruction and object recognition method and from specified model parameters (MP1, MP2, ...), the at least one object comprising the trailer, - a movement vector (1BV5, 2BV5) to the at least one prominent point (KP1) on the trailer is determined from the camera image by means of a Bayes estimate or by means of a method for recognizing a position of discontinuity, - the most probable position (PK) of the at least one prominent point (KP1) is determined from the object position (P5) and the determination of the movement vector (1BV5, 2BV5), the most probable position (PK) of an edge of the trailer being determined as a value for which an a posteriori probability obtains a maximum value. - the image portion being updated in accordance with a most probable position (PK) of at least one prominent point (KP1) on the trailer , characterized in that the following is carried out to determine the most probable position (PK): - a three-dimensional model with the object position (P3, P5, P8) of at least one object from the camera image (104, KB) is determined by means of a surround reconstruction and object recognition method and from specified model parameters (MP1, MP2, ...), the at least one object comprising the trailer, - a movement vector (1BV5, 2BV5) to the at least one prominent point (KP1) on the trailer is determined from the camera image by means of a Bayes estimate or by means of a method for recognizing a position of discontinuity, - the most probable position (PK) of the at least one prominent point (KP1) is determined from the object position (P5) and the determination of the movement vector (1BV5, 2BV5), the most probable position (PK) of an edge of the trailer being determined as a value for which an a posteriori probability obtains a maximum value. - a three-dimensional model with the object position (P3, P5, P8) of at least one object from the camera image (104, KB) is determined by means of a surround reconstruction and object recognition method and from specified model parameters (MP1, MP2, ...), the at least one object comprising the trailer, - a movement vector (1BV5, 2BV5) to the at least one prominent point (KP1) on the trailer is determined from the camera image by means of a Bayes estimate or by means of a method for recognizing a position of discontinuity, - the most probable position (PK) of the at least one prominent point (KP1) is determined from the object position (P5) and the determination of the movement vector (1BV5, 2BV5), the most probable position (PK) of an edge of the trailer being determined as a value for which an a posteriori probability obtains a maximum value. <EOS>