Q: Are accidents or other types of events removed from the AIS point data?
A: Collisions and accidents are not removed from the data explicitly. The MarineCadastre.gov AIS data represent 16 of the most important fields from the original AIS record. Our data are filtered to a one-minute rate and show all vessels that the land-based antennas received, with the exception of certain law enforcement and military vessels that are excluded.
Q: Do you have tonnage, horsepower, fuel type, and other parameters for vessels?
A: No, these parameters are not part of our database. We have heard about other users finding these parameters in commercial databases, and having success in merging those parameters with the Marine Cadastre AIS records using the MMSI value as a JOIN key.
Q. Do you have a voyage identifier value?
A: Before 2015, we did calculate and insert a voyage ID and included the destination value. Our criteria for defining a voyage can be found in the AIS Data Handler documentation. Since 2015, we have not included a voyage ID or destination because defining the start and end of a voyage is a subjective and complex process dependent on mariner input. The Track Builder tools are now the best option to generate track lines that can be used to define a voyage.
Q: Do you have origination or destination values?
A: We collect the destination values; however, most of the entries are incomplete, inconsistent, or null. We will continue to monitor the destination and the origination input and will consider adding them to future products if the values are more complete.
Q: How do I interpret the vessel codes and cargo codes?
A: The vessel type codes are outlined in this PDF document. The cargo codes are part of the vessel type parameter. Please see the detailed documentation available at the U.S. Coast Guard, Navigation Center.
Q: How do the vessel draught field from 2009 to 2014 and the vessel draft field from 2015 to 2017 compare?
A: The 2009-2014 draught parameter is reported in 1/10’s meters, and the value 255 equals 25.5 meters or greater. The 2015-2017 vessel draft parameter is reported in meters. Carriage requirements and instructions to mariners for entering vessel draft values have changed over time. Recent vessel draft values report the “maximum present static draught.”
Q: If I want to group data by vessel type, can I combine vessel type codes? For example, should I combine vessel type 31 (towing) with vessel type 1025 (towing vessel)?
A: In this example, yes.
We have used the U.S. Coast Guard Authoritative Vessel identification Service (AVIS) to populate and improve many of the null values found in the native AIS data. Similar vessel types from both lists can be combined into groups. We usually categorize null values under the “other” group type. We have also found many users have a need to define their own groups of vessel types. The vessel groups defined by MarineCadastre.gov are those frequently used among the ocean planning community.
- Codes 0 through 255 are original vessel type codes defined by AIS standards
- Codes 256 through 999 are an empty set added by MarineCadastre.gov
- Codes 1001 through 1025 are keys to the AVIS vessel type descriptions
Q: Who owns the copyright to these AIS data, and are they available for use and redistribution by commercial entities?
A: Our data are derived from the U.S. Coast Guard NAIS and are free for public use. The MarineCadastre.gov AIS data are intended for coastal and ocean planning. Please see the information at the bottom of the NAIS web page for the terms and conditions of use. If you have additional questions about the terms and conditions, please use the contact email on the NAIS data request page.
Q: Are the AIS data provided by MarineCadastre.gov adequate for regulatory or enforcement purposes?
A: The AIS data provided by Marine Cadastre are intended for marine planning purposes only.
Q: What is the resolution (cell size) of the density grids?
A: The cell size for the kernel density grids (2011 and 2013) is 100 meters. The cell size for the transit count grids (2015, 2016, and 2017) is 100 meters.
Q: Why are there AIS points over land (e.g., like Kansas and Canada in data set 2017_01_Zone14)?
A: Location values are principally derived from on-vessel GPS devices. For a detailed discussion on errors in GPS signals, please search the web or contact a vendor of GPS units. Accurately reported GPS positions from vessels being transported over land can also be seen in the data, as well as vessels transiting very small canals and locks that may be difficult or impossible to see on a web-map.
Q: How do I account for apparent inconsistencies of the AIS timestamp and of an observed vessel’s voyage?
A: The full timestamp is added to the record by the base station, using the time clock of the base station that is reporting in UTC. Be sure to account for your time zone shift to UTC and other offsets such as Daylight Savings Time.
Q: Is there a schema diagram or data dictionary for the new AIS points data?
A: Below is the proposed data dictionary starting in 2018. This expands the 2015, 2016, and 2017 data with the addition of the Transceiver Class designation.
Q: What does a value of “511” in the Heading field represent?
A: The value 511 stands for “not available = default.”
Q: What is represented by Vessel Type code 59, and what is RR Resolution No. 18 referencing?
A: A good place to begin researching the meaning of type codes and resolutions is on the U.S. Coast Guard Navigation Center website (see IMO Resolutions).
Q: How can I calculate the estimated time of arrival (ETA) for vessel tracks?
A: While there are multiple ways one could calculate ETA values, here is just one suggestion:
- Filter the points to remove unwanted vessels or vessel types.
- Generate vessel tracks, probably using a 24-hour period to segment the tracks.
- Generate a polygon defining the arrival port.
- Examine track end-time date/times of the remaining tracks.
Note: Track start and end times are contained within the MarineCadastre.gov trackline data sets
Note: Track start and end times are contained within trackline products generated by the Track Builder tools
Q: I am failing to create tracklines for points that are very close together (for example, less than 10 meters). How do I create tracklines in these cases?
A: This is due to how the python script handles XY points that are very close together (~10 meters or less) AND are stored in a geographic coordinate system (GCS). If the points are first transformed into a projected coordinate system, the python script runs as intended and will connect the points even when they are in very close proximity to one another.
The TrackBuilder input file should be in a projected coordinate system if there is a need for points closer than ~10 meters to be connected. If very near points do not need to be connected, then either projected or geographic coordinate systems can be used for an input file.
Q: Why do I encounter failures or errors when running the Track Builder tool (v3.1)?
A: Error messages that say you have run out of memory while the tool is running could be due to using the 32-bit version of the tool or environment (such as IDLE). The best solution is to use the 64-bit command line version of the program. You will need to have the 64-bit Background Geoprocessing patch installed. The patch will install a 64-bit version of Python for ArcGIS Desktop. If you are running ArcGIS Pro, be sure to use our Track Builder Pro 1.0 tool.
Q: When working AIS data prior to 2015 in the file geodatabase format, clipping the broadcast features to an area of interest causes the link between the features and the voyage attributes to be broken within the Track Builder. How do I retain these voyage attributes?
A: The Track Builder tool looks for specific field names in the Vessel and Voyage tables that match the data model used in the MarineCadastre.gov products. Check during your CLIP process that file or field names are not being modified. Consider using a simple JOIN of the Vessel and Voyage tables using the MMSI as key after you run the Track Builder tool.
Q: I am not an ArcGIS user. How can I access and use the 2009 to 2014 data that are in the file geodatabase format?
A: Consider using the GDAL Python library, which supports a wide range of file format translations and other operations that can be run from the command line. Numerous commercial applications by companies such as SAFE Software and MatLab have a capacity to read the native GDB format. Reference their documentation for which version is supported.
Q: Do you include Class B data?
A: Beginning in 2018, we will include class B data and the class designation for each record.
Q: Do you have AIS for [my location]?
A: The AIS data published by MarineCadastre.gov originates from the Nationwide Automatic Identification System (NAIS) by the U.S. Coast Guard. The NAIS is composed of approximately 200 land-based receiving stations located near important navigation routes in the conterminous U.S., Alaska, Hawaii, Guam, and parts of the Caribbean. NAIS data are generally not available for the Arctic, waters beyond 40 to 50 miles of the coast, or foreign waters.
Q: Do you have AIS data collected by satellite?
A: No. All of our data originates from land-based receivers. Commercial providers collect, license, and sell satellite AIS data. Some federal agencies purchase satellite AIS data for specific needs, and they are restricted from distributing the data to the public by the terms of their license agreement.
Q: Do you have AIS data before 2009?
A: No, 2009 is the earliest data we have.
Q: Do you have plans to publish data for this year?
A: Every year the MarineCadastre.gov team prioritizes data development activities based on funding and needs expressed by the user community. Please let us know how you are using the AIS data by emailing firstname.lastname@example.org, and if annual releases are necessary. This will help us prioritize and plan future releases.