The department may, on behalf of the state, contract with the United States government for the aerial photographing and mapping, scale of photographs and maps, determining the method, form, and execution of maps, and all other details of the work necessary to prepare base maps of those portions of the state as may be agreed upon. The state shall receive negatives of all aerial photographs and copies of all base maps prepared. The maps shall be prepared so as to show the location of roads, railroads, streams, canals, lakes, rivers, timbered areas, and all other natural and artificial features capable of being mapped by the methods to be mutually agreed upon by the geological surveys of the state and the federal government. The state shall not contract to pay more than the amounts paid by the federal government for these purposes. For the purpose of making these surveys, persons employed in making the surveys may enter at reasonable times upon all parts of all lands within the boundaries of this state, but this part does not authorize any unnecessary interference with private rights or the performance of any act not necessary for the preparation of the base maps.