Abstract: In connection with the segmenting of a digital image divided into small elements (pixels) and acquired with a camera having several colour channels, to discern an object from a background, the daylight locus and the colour locus of the camera are, a priori, modelled after to the body reflectance characteristic of the subject. In this way a normal vector (nS) to the daylight locus is determined a priori and for each pixel, the scalar product between a colour vector (cf) of the element in the form of the response from the colour channels of the camera and the normal vector of the daylight locus is calculated, following which the element is characterized as representing object or background on basis of the calculation result, the elements characterized as objects (1) being assigned one value and the elements characterized as background being assigned a second value. On basis of the segmented image a control signal for an implement (4) is derived.

Abstract: According to the method a laser light source (10), which in a beam direction (14) exposes a line (13), and a light detector (9) capable of taking a picture with a certain resolution and having a line of sight (12), are mounted on a vehicle (1) or implement (5) with a travelling direction (P) in such a manner that a line (13) exposed by the laser light source (10) in the field is transverse to the travelling direction (P), that the light detector (9) aims at the line (13) exposed by the laser light source (10), the line of sight (12) of the light detector (8) and the beam direction (14) of the laser light source (10) forming an angle (alpha) in a plane transverse to the exposed line (13). The light detector (9) takes a picture of the exposed line (13) and the picture taken by the light detector (9) of the exposed line (13) in the field is analysed with a view to determining extreme value points (18), bends or the like characteristics in the picture of the line (13).