The tides at Inchon have an average range of and a maximum observed range of , making the tidal range there one of the largest in the world and the littoral maximum in all of Asia. Clark observed the tides at Inchon for two weeks and discovered that American tidal charts were inaccurate, but that Japanese charts were quite good. Clark's team provided detailed reports on KPA artillery positions and fortifications on the island of Wolmido, at Inchon and on nearby islands. During the extensive periods of low tide, Clark's team located and removed some North Korean naval mines, but, critically to the future success of the invasion, Clark reported that the North Koreans had not in fact systematically mined the channels.