Okla. Stat. tit. 69 § 702
The Department, through its authorized agents and employees, may enter upon any lands, waters, and premises in the state for the purpose of making surveys, soundings and drillings, and examinations as may be determined necessary or convenient for the purpose of establishing, locating, relocating, constructing, and maintaining state highways or relocations thereof and facilities necessary and incidental thereto. Such entry shall not be deemed a trespass, nor shall an entry for such purpose be deemed an entry under any condemnation proceedings which may be then pending; but notice shall be given to the owner of or person residing on the premises, personally or by registered mail, at least ten (10) days prior to such entry.
Okla. Stat. tit. 69, § 702