Two-step locating system for harsh marine port environments

With the increasing amount of traffic volume on containers, not only identification but also location estimation of assets has become an important issue in logistics automation in a port environment. The locating system is generally composed of tags, readers, and a location engine. Tags are attached to the object and obtain information via communication with readers that are installed around the tags. The engine continuously attempts to estimate the location of tags by using the obtained information. However, if we attempt to apply this common locating system to a port environment for logistics automation, the system performance is degraded because there are many steel obstacles that cause interference in the RF communication and measurement. In this paper, we propose a two-step approach for location estimation in harsh port environments. We divided readers into two types (fixed and mobile readers); hence, the location method operates in two steps for efficient wireless communication and precise measurement. We implemented all the system components and installed these at a real port for evaluation. The communication and estimation success rate is more than 50% better than that of the existing general locating system, and the location precision is substantially increased.