2011 Tug Towing Vessel Density

Automatic Identification Systems (AIS) are a navigation safety device that transmits and monitors the location and characteristics of many vessels in U.S. and...自动识别系统（Automatic Identification Systems，AIS）是一类航行安全设备，可用于传输并监测美国及……范围内诸多船舶的位置与航行特性。