Information Technology Reference
In-Depth Information
Canals, straits, strategic passages
: The original data contain several places that
are not container ports or even seaports, such as canals (Panama, Suez), straits
(Gibraltar, Dover, Dardanelles, Messina), channels (Yucatan), and other passage
points at which the vessel reported a call (e.g., Tarifa and Cape Finisterre on
the Iberian peninsula; Skaw in Denmark; Brixham in the UK). While such
“nodes” are part of the effective movement of vessels, they do not account for
port commercial operations, nor are they part of voluntarily selected logistics
routes or transport chains. Because almost all pendulum services pass through
the Panama and Suez canals, their centrality in the graph would go beyond those
of the biggest commercial ports. Thus, they were omitted from the data
5
.
Direct or indirect inter-port connections
: An analysis based on direct connections
would imply a simplification of the reality of shipping networks. Although
direct connections provide useful insights into the way ports are related to their
close neighbors, liner networks are built upon a majority of indirect calls. Line-
bundling and hub-and-spoke
6
are the most common services provided by ocean
carriers willing to extend their influence across trading areas and continents.
Thus, vessels are operated through rotating patterns that make an analysis based
on indirect linkages more relevant. In addition, direct linkages may deprive some
ports of their true foreland extent: a direct degree of 2 may hide an indirect degree
of 30 if the port is connected to wide international logistics chains.
The methodology for building the graph consists of retrieving for each port all
its direct and indirect connections through the circulation of each vessel during
1 year, regardless of the exact time of the connection. This enables Rotterdam
to be connected with Tokyo, although in reality, those two ports are not directly
connected by a single voyage; usually, pendulum services run for 3 weeks between
Europe and Asia through the Suez Canal, including many intermediate calls. In
the end, every vessel's circulation creates a complete graph in which all ports are
fully interconnected. The resulting world graph is therefore a combination of all
individual vessels' complete graphs.
5
Other nodes that are commercial ports such as Istanbul (Turkey) and Port Said (Egypt) were also
omitted because of their enormous number of calls compared to their actual traffic. Their proximity
to important strategic passages has caused them to be reported by many vessels, although not
every call represents a commercial operation at the terminals. Other cases include Brunsbuttel
(Germany), a port at the mouth of the Elbe River, whose calls were attributed to Hamburg, the
actual destination. Finally, some terminals have been merged in the data with their representative
port, such as Port Botany and Sydney (Australia).
6
The hub service is a combination of line-bundling and local services centralized upon one main
transshipment center. A mother vessel calls at a transshipment hub where containers can be
transferred to another mother vessel (i.e., interchange) or to a feeder vessel that carries out the
rest of the local or regional service (
Brocard et al.
,
1995
). There are a few round-the-world (RTW)
services where ships are bigger. Other services are pendulum services such as Europe-Asia and
local services such as Rotterdam-United Kingdom. Line-bundling services often connect different
global regions while hub-and-spoke services are more intra-regional.
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