EMODnet Human Activities, Vessel Density Map
The Vessel Density maps in the EU are created since the 2019 by Cogea for the European Marine Observation and Data Network (EMODnet). The dataset is updated every year and is available for viewing and download on EMODnet Human Activities web portal (https://emodnet.ec.europa.eu/en/human-activities). The maps are based on AIS data yearly purchased from Collecte Localisation Satellites (CLS) and ORBCOMM. The maps, GeoTIFF format, show shipping density in 1x1km cells of a grid covering all EU waters and some neighbouring areas. Density is expressed as hours per square kilometre per month. The following ship types are available:0 Other, 1 Fishing, 2 Service, 3 Dredging or underwater ops, 4 Sailing, 5 Pleasure Craft, 6 High speed craft, 7 Tug and towing, 8 Passenger, 9 Cargo, 10 Tanker, 11 Military and Law Enforcement, 12 Unknown and All ship types. Data are available by month of year. Yearly averages are also available.
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Re-use of content for commercial or non-commercial purposes is permitted free of charge, provided that the sources (both EMODnet - Human Activities, and CLS) are acknowledged. EMODnet - Human Activities accepts no responsibility or liability whatsoever for the re-use of content accessible on its website.
['-87.706484', '97.633027', '14.961111', '86.842727']
0f2f3ff1-30ef-49e1-96e7-8ca78d58a07c (metadata download)
Marine Layer ; Marine Waterway ; Transport Area ; INSPIRE feature concept dictionary (Version: Linked Data 1.0) ;
merchant shipping ; maritime navigation ; maritime transport ; GEMET (version 3.1, 2012-07-20) ;
Transport networks ; Geographical grid systems ; GEMET - INSPIRE themes, version 1.0 ;
AIS data are annualy purchased from two commercial providers, CLS and ORBCOMM. The data consists of messages sent by automatic tracking systems installed on board ships and received by terrestrial and satellite receivers alike. The acquired datasets currently cover a period from 2017 to 2021 for an area covering all EU waters. A partial pre-processing of the data is carried out by CLS: (i) The only AIS messages delivered are the ones relevant for assessing shipping activities (AIS messages 1, 2, 3, 18 and 19). (ii) The AIS data are down-sampled to 3 minutes (iii). Duplicate signals are removed. (iv) Wrong MMSI signals are removed. (v) Special characters and diacritics are removed. (vi) Signals with erroneous speed over ground (SOG) are removed (negative values or more than 80 knots). (vii) Signals with erroneous course over ground (COG) are removed (negative values or more than 360 degrees). (viii) A Kalman filter is applied to remove satellite noise. The Kalman filter is based on a correlated random walk fine-tuned for ship behaviour. The consistency of a new observation with the modelised position is checked compared to key performance indicators such as innovation, likelihood and speed. (ix) A footprint filter is applied to check for satellite AIS data consistency. All positions which are not compliant with the ship-satellite co-visibility are flagged as invalid. The AIS data are converted from their original format (NMEA) to CSV, and deliverd to Cogea split into 12 files, each corresponding to a month of the year. By running a series of commands from Linux shell, all remaining invalid characters are removed as well as unnecessary fields. The data are then imported into a PostgreSQL relational database (with the PostGIS extension), each month in a different table containing the following specialised data types: mmsi (numeric), locdate (date), loctime (time without time zone), lon (double precision), lat (double precision), aisshiptype (character varying). MMSI numbers are often associated to more than a ship type during a year. To cope with this issue, a unique MMSI/ship type register is created every year. In the register, MMSI with multiple ship types are associated the most recurring ship type by counting the number of record for each combination mmsi/ship type. The admissible ship types reported in the AIS messages are grouped into macrocategories: 0 Other, 1 Fishing, 2 Service, 3 Dredging or underwater ops, 4 Sailing, 5 Pleasure Craft, 6 High speed craft, 7 Tug and towing, 8 Passenger, 9 Cargo, 10 Tanker, 11 Military and Law Enforcement, 12 Unknown and All ship types. The subsequent steps consist of creating points representing ship positions from the AIS messages, then reconstructing ship routes (lines) from the points for every two consecutive positions of a ship, by using the MMSI number as a unique identifier of a ship. In addition, for each line the query calculates its length (in km) and its duration (in hours) and append them both as attributes to the line. If the distance between two consecutive positions of a ship is longer than 30 km or if the time interval is longer than 6 hours, no line is created. Both datasets (points and lines) are projected into the ETRS89/ETRS-LAEA coordinate reference system, used for statistical mapping at all scales, where true area representation is required (EPSG: 3035). Points and lines calculations are based on custom-made sql scripts developed by Cogea. The lines obtained are then intersected with a custom-made 1x1km grid polygon (21 million cells) created by Cogea, based on the EEA's national grids, extended to cover the whole area of interest (all EU sea basins) and imported in PostGIS. Because each line has length and duration as attributes, it is possible to calculate how much time each ship spent in a given cell over a month by intersecting line records with grid cell records. This is done through a custom-made sql script developed by Lovell Johns. Using the PostGIS Intersect tool, for each cell of the grid, the time value of each 'segment' in it is summed, thus obtaining the density value associated to that cell, stored in calculated PostGIS tables. Density is thus expressed in hours per square kilometre per month. The final step consists of creating and compressing raster files (TIFF file format) with QGIS and GDAL from the PostGIS vessel density tables. Annual average rasters by ship type are also finally calculated. For more details on vessel density concepts see the full method published at: https://www.emodnet-humanactivities.eu/documents/Vessel%20density%20maps_method_v1.5.pdf. Comparared with the original method's calculations, from the 2021 (2020 data) the calculations of ship positions (points) and ship routes (lines) were sped up by moving them from ArcGIS to PostGIS.