1. A method for automatically determining a boundary, comprising: dividing, by a processor, a total area of a map into a matrix of rectangular area segments; determining a partial area of the map, the partial area being associated with a connected subset of the rectangular area segments, the partial area being determined using an algorithm that determines a remaining range of a motor vehicle; initially starting from a region of the total area not belonging to the partial area, finding a first boundary area segment of the partial area; entering a first point describing a position of the first boundary area segment into a list of points; after entering the first point, stepping along an edge of the partial area; for each further boundary area segment that is found, entering a corresponding further point describing a position of the further boundary area segment into the list of points; and when the first boundary area segment is reached again, determining the boundary from the list of points.