eNav8 AIS coverage definition

By Brian at September 22, 2010 05:58
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EfficienSea submitted an input paper with a suggested definition of AIS coverage.  They recognized a need for a definition as they work to provide e-Navigation services through their test bed in the Baltic Sea area.  If you advertise the availability of services, you need to be able to determine the level of service you can provide.  For services depending on AIS, coverage is a key part of the level of service - you cannot provide AIS-based services outside of your AIS coverage area.
The definition EfficienSea came up with is:

where QAIS is:

We provided a variety of comments, in summary:

-    Recommended that the definition be separated to define “AIS receive” (i.e., receipt ashore of AIS messages from ships) and “AIS transmit” (i.e., ship receipt of AIS messages transmitted from shore stations).
-    Another definition of coverage area may be needed to measure ship-to-ship AIS coverage, as this would be critical to preserve the navigation safety aspect of AIS.
-    Levels of AIS service should be matched with the specific services provided;  e.g., the level of service for provision of traffic organization services  would be higher than that required for information services.
-    Coverage may be measured using a variety of criteria, including:
AIS receive:
•    AIS report rate, i.e., the frequency of receipt of reports from vessels by a base station
•    Distance traveled between reports, i.e., the distance travelled by a vessel between receipt of AIS reports
•    Percentage of receipt, i.e., AIS reports received by a shore station vs. number of reports expected to be received from vessels based on their speed, rate of turn, etc.
AIS transmit:
•    Probability of receipt of a message transmitted by a base station by a vessel within a defined distance from the base station
•    Basic coverage area should be determined using calculation of the expected RF coverage area, given a defined power level, antenna height, etc.
-    It was noted that receive coverage will vary based on the AIS installation on the vessel (e.g., height of antenna, quality of installation, power of transmitter), and the type of AIS (i.e., Class A vs. Class B)

This input will be provided to EfficienSea as they continue their work, and the final definition will ultimately be included in the appropriate IALA recommendation or guideline (possibly the draft IALA guideline “An Overview of AIS” which we are also working on this week).