The board of supervisors may provide and pay from county funds for the making or purchase of the maps and block-books by contract with some other competent person, if any of the following conditions exist:
(a) The office of the assessor is not provided with maps and block-books.
(b) The maps or block-books in the office of the assessor are insufficient or defective and the surveyor neglects or refuses to make them.
(c) The facilities of the surveyor’s office are inadequate to do so.