Method for updating a digital road map which contains, for at least one mapped road, respective spatially resolved description values of at least one mapped environment property, wherein, in order to update the road map, in each case at least one graph (16, 16') of concatenated data sets describing a respective real journey of the motor vehicle is received by a processor circuit from at least one measuring motor vehicle, wherein in each graph (16, 16') of concatenated data sets each individual data set specifies, for a geoposition that was passed during the journey, at least one measurement value recorded at this geoposition for a new or already mapped environment property, wherein a virtual journey along the at least one mapped road is simulated by the processor circuit before updating on the basis of the road map which is already available and is to be updated, by a respective virtual measurement value of the at least one environment property already mapped in the road map being determined for different virtual geopositions from the road map, wherein such a virtual measurement value corresponds to a description value from the road map or to an interpolation value from a plurality of the description values, and at the virtual geopositions a concatenated data set which describes the virtual journey is produced from the virtual measurement values, and the received concatenated data sets of the respective real journey of the at least one motor vehicle and the concatenated data sets of the virtual journey are combined and the updated road map is calculated from the combined data sets, wherein the updated road map is calculated by calculating, from the measurement values (15, 15') and the associated geopositions (21, 28) of the concatenated data sets of the respective real journey and the concatenated data sets of the virtual journey, updated, spatially resolved description values of the respective environment property described by the measurement values (15, 15'), wherein at a respective geoposition (21, 28) an average value of the measurement values (15, 15') associated with this geoposition because they were measured at this geoposition or in a predetermined region around this geoposition is calculated or a statistical distribution of the measurement values (15, 15') and therefrom the respective description value is determined, and wherein the road map is iteratively updated based on concatenated data sets received sequentially in time. a virtual journey along the at least one mapped road is simulated by the processor circuit before updating on the basis of the road map which is already available and is to be updated, by a respective virtual measurement value of the at least one environment property already mapped in the road map being determined for different virtual geopositions from the road map, wherein such a virtual measurement value corresponds to a description value from the road map or to an interpolation value from a plurality of the description values, and at the virtual geopositions a concatenated data set which describes the virtual journey is produced from the virtual measurement values, and the received concatenated data sets of the respective real journey of the at least one motor vehicle and the concatenated data sets of the virtual journey are combined and the updated road map is calculated from the combined data sets, wherein the updated road map is calculated by calculating, from the measurement values (15, 15') and the associated geopositions (21, 28) of the concatenated data sets of the respective real journey and the concatenated data sets of the virtual journey, updated, spatially resolved description values of the respective environment property described by the measurement values (15, 15'), wherein at a respective geoposition (21, 28) an average value of the measurement values (15, 15') associated with this geoposition because they were measured at this geoposition or in a predetermined region around this geoposition is calculated or a statistical distribution of the measurement values (15, 15') and therefrom the respective description value is determined, and wherein the road map is iteratively updated based on concatenated data sets received sequentially in time.