HIFLD OPEN Warning Signal Stations (USACE IENC)

The USACE IENCs coverage area consists of 7,260 miles across 21 rivers primarily located in the Central United States. IENCs apply to inland waterways that are maintained for navigation by USACE for shallow-draft vessels (e.g., maintained at a depth of 9-14 feet, dependent upon the waterway project authorization). Generally, IENCs are produced for those commercially navigable waterways which the National Oceanic and Atmospheric Administration (NOAA) does not produce Electronic Navigational Charts (ENCs). However, Special Purpose IENCs may be produced in agreement with NOAA.

美国陆军工程兵团（United States Army Corps of Engineers, USACE）内河电子航海图（Inland Electronic Navigational Charts, IENCs）的覆盖范围横跨美国中部地区的21条河流，总长度达7260英里。此类内河电子航海图适用于由美国陆军工程兵团维护、供浅吃水船舶航行的内河航道（例如，航道维护水深为9至14英尺，具体标准依航道工程授权文件而定）。通常而言，内河电子航海图的制作范畴为美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration, NOAA）未编制电子航海图（Electronic Navigational Charts, ENCs）的商业通航航道。不过，在与美国国家海洋和大气管理局达成协作协议的前提下，亦可制作专用内河电子航海图。