It shall be the duty of the county board of each organized county in the State of Nebraska to cause to be surveyed, by a competent surveyor, all irregular subdivided tracts or lots of land, other than regular government subdivisions, and cause the same to be platted on a scale of not less than ten inches to the mile; Provided, however, where any county has in its possession the correct field notes of any such tract or lot of land, a new survey shall not be necessary, but such tracts may be mapped from such field notes.