A method and device for optimizing a parameter of a combine harvester by driving the combine harvester over a field an approximately constant speed or constant throughput； determining and storing data pertaining to at least one sensor value for a parameter of the processing procedure and to the associated position of the combine harvester in a processing unit； transmitting the position data to a manual apparatus provided with a camera and with a position determination device； moving the manual apparatus to the position, and recording an image of the field ground with a camera； processing the image in order to determine a property of the image； determining a calibration value by the processing unit using the sensor value and the property； and displaying and/or automatic setting of an operating value of the combine harvester by the processing unit using current sensor values and the calibration value.
