The invention relates to a method for marking sports field by placing stripes of paint according to a predefined plan via a spraying nozzle on a level playing surface such as grass, gravel, ice, artificial grass or synthetic material field. A robot unit is provided that is configured to move along the stripes according to the predefined plan. The robot unit receives signals from a number of GPS sending units and continuously calculates its current position on the sports field, and uses the current position on the sports field to calculate a set of control signals to two or more movable elements for propulsion of the unit and for controlling the emission of paint. The invention also relates to a robot unit and use of a robot unit for marking fields.
展开▼