Ohio Revised Code Title XV. Conservation of Natural Resources § 1507.13

The chief engineer of the department of natural resources or any employee in the service of the division of engineering may enter upon lands to make surveys and inspections in accordance with this chapter when necessary in the discharge of the duties specified in this chapter. Notice of such a proposed entry shall be given to the owner of the land to be surveyed or inspected or to the person in possession of it by such means as are reasonably available, not less than forty-eight hours nor more than thirty days prior to the date of the entry. Such an entry does not constitute a trespass.