# Towards a Reference Architecture for Cargo Ports
## 2 Background
### Cargo Ports
#### 2.2.3 Container Terminal Operations  
Figure 3 presents a modern container terminal [34]. Container terminals work day and night, and their workload depends on the number of containers in transit. Containers arrive at the terminal by trains, ships, or trucks and are stored in the terminal yard. Then, they leave the terminal by the same means to reach their final destination [35]. A ship-to-shore crane (STS) is a crane that services a container ship by shifting on a rail to reach the assigned stowage within the same ship and also to move from one ship to the next once the first one has been completed. STS cranes provide the single most important operation (called a move) associated with the loading and unloading of a ship and are the only means of moving containers to or from a ship [36]. To unload a ship, one or several STS cranes pick up containers from the ship and put them on trailers or shuttle trucks that move them to the assigned yard positions within the terminal storage area. Automated guided vehicles (AGV) are also used for the transport of containers from the dock to the yard. To load a ship, the STS crane unloads a container from the trailer and puts it in the ship. In automated or semi-automated container terminals, this operation is performed by crane operators controlling ship-to-shore cranes (STS) from a control room. Optical character recognition (OCR) technology is used to automatically read and record the container's ISO code identification number as it is handled by an STS crane. By automating the handoff of containers from cranes to vehicles, the process becomes safer for people as there is no need for checkers or tally workers under the cranes who are responsible for recording container numbers. More advanced features include damage images, door direction, hazardous labels, and reading and reporting the drayage truck numbers onto which the container is transferred [37]. Figure 2: Cargo port system package diagram. Containers stacked in a ship are secured in several ways to prevent them from being damaged at sea. Locking corner castings are placed between stacked containers in non-cellularized ships to align the containers and provide a place to brace them. The cross braces are then secured to the floor of the ship, and, finally, the hatch covers are put back in place. Cellularized ships do not require corner castings or cross braces since permanent guides and locks (which allow containers to be stored more densely than in non-cellularized cargo vessels) are already on board [35; 36]. Operations in the storage yard are more flexible than STS crane operations. In a storage yard, gantry cranes, top-pick loaders, or straddle carriers are used to stack containers. Automated stacking cranes (ASC) are also used. Other transport vehicles include automated lifting vehicles and unmanned shuttle carriers able to locate the containers and pick them up from the ground [37]. Automated vehicles may share a common software control module at the equipment level, often referred to as the equipment control system (ECS), for handling, for example, safety features and intra-vehicle coordination. An ECS is defined as the software that monitors and controls all events and processes at the equipment level, either for a single piece of container handling equipment (CHE) such as an AGV or a group of CHE. ECS coordinates interactions between different types of automated equipment [33; 37; 38]. The container storage area is usually separated into different stacks (or blocks) that are differentiated into rows, bays, and tiers. Some stack areas are reserved for special containers like reefers (refrigerated containers), which need electrical connections, dangerous goods, or overweight/overwidth containers, which do not allow for normal stacking. Often, stacks are separated into areas for import, export, and empty containers. Even with these many subdivisions, the efficiency of storage yard equipment is greatly increased by being able to store only one portion of the yard at a time.