The Inland Electronic Navigational Charts (IENC) dataset is updated once every 2 weeks, and is from the US Army Corps (USACE)/Army Geospatial Center (AGC), and part of U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics’ (BTS’) National Transportation Atlas Database (NTAD). These IENCs were developed from available data used in maintenance of Navigation channels. These vector data that comprise the charts can be downloaded as a geodatabase, here: http://ienccloud.us/ienc/products/files/U37/ienc_master_dataset_gdb/USACE_IENC_Master_Service_gdb.zip. In addition, web mapping services of the feature classes/datasets can be found here: http://ienccloud.us/arcgis/rest/services/IENC_Feature_Classes Users of these IENCs should be aware that some features and attribute information could have significant inaccuracies due to changing waterway conditions, inaccurate source data, or approximations introduced during chart compilation. Chart data distributed from this website should not be used for navigation.  Only charts downloaded from the USACE chart server, https://ienccloud.us, and used in an Electronic Chart Display Information System (ECDIS) or Electronic Chart System (ECS), or official government chart books are suitable for navigation.