Data: Ship Types
There are 325 ships on GreenFerries at the moment. Our sources of data are THETIS and Wikipedia. This page explains how we filter ships from these data sources.
Filter on THETIS types
The THETIS database contains information about 14968 ships.
Most of the ships present in THETIS are not passenger ferries but industrial ships. There is a "Ship Type" column in THETIS that we use to filter ships upon. Here is the distribution of ships based on that type.
We only keep "Ro-pax" and "Passenger ship" ships for now, which gives us a total of 605 ships. We are voluntarily discarding "Ro-ro" ships because we care only about passenger ferries, not ferries carrying only vehicles (they are not an alternative to planes).
Filter ships present in Wikipedia
Wikipedia contains extremely precious info about many ships: operating company, route itineraries, passenger capacity, photos etc... So far, we're only presenting ships that we could link to a Wikipedia page in order to get this qualified data.
We automated extracting data from Wikipedia through the Wikidata query service. We get data about 6538 ships with a unique IMO.
Based on the ships IMO we compute the intersection of the 605 passenger ships in THETIS and 6538 ships in Wikipedia, which gives us a total of 528 ships.
Out of scope ships
Among these 528, we manually marked 187 ships as "out of scope", meaning that they are not passenger ferries. Most are cruise ships, which are out of scope as their main purpose is not to travel, or at least they are not a reasonable option to travel responsibly. Some other are ships incorrectly categorized, for example some Ro-pax ships are converted to Ro-ro. Others are not in action anymore.