Every railroad company, as aforesaid, before proceeding to construct any such extension of its railroad or branch railroad into or through any county mentioned in said resolution of its board of directors, shall make a map or maps of the route intended to be or already adopted for such extension or branch railroad by such company in such county or counties, which map or maps shall show all details as required by section 388.330, and shall be certified by the president or vice president and engineer of said company, or by a majority of the directors, and filed in the office of the clerk of the county commission of each county into or through which the extension of said railroad or said branch railroad is intended to be constructed. The company shall give written notice to all actual occupants of the land over which the route of said extension or branch railroad is so designated, and which has not been purchased by or given to said company.