The bathymetry of Cook Inlet is unusually well-described for an Alaskan area, with a majority of the relevant surveys conducted since 1964, and the entire area well-surveyed except for some of the northern mud flats. Part of the reason for this wealth of information is that Cook Inlet is home to Alaska's largest city, Anchorage, which includes significant shipping routes and several active oil rigs. Approximately 11% of the area has also been mapped with multibeam acoustic methods in six sections, providing modern, higher resolution data. Still, there have been a number of obstacles for surveyors of all eras to overcome as noted in the Descriptive Reports for earlier National Ocean Service (NOS) hydrographic surveys, including rough weather (H03431/H03432), winter ice in the north end (H03431/H03432), "steep banks breaking off and falling into the water sounding like small explosions of dynamite" (H03431/H03432), large tidal range (H03431/H03432), a tidal bore 3 to 6 ft high (H03431/H03432), strong currents up to 8 knots (H03203), shifting channels (H03431/H03432), dangerous shoals (H03044), extensive mud flats (H03431/H03432), and atmospheric refraction causing superior mirages of landmarks on clear days (H03203). Later surveys also noted the difficulties caused by areas of sand waves