Automatic Identification System
Type A AIS is mandatory for vessels over 300 tonnes under SOLAS V regulations. Type B introduced as a cheaper voluntary system for all other non mandatory vessels. Turkey made a upgraded type B mandatory fit for all commercial passenger carrying vessels over 10 metres from Mid 2009. This includes foreign flag vessels requiring a 'seaworthiness certificate' which includes charter boats.
Type B recievers are available for around €150 which will recieve type A & B transmissions.
Example of type B transmission
Navigation programs can calculate in real time the CPA & TCPA. (Closest Point of Approach & Time to Closest Time of Approach) using the received AIS dat and its own position derived from the onboard GPS. This has given rise to the expression "AIS Radar" because of its similarity to the information provided by modern ARPA & MARPA Radar systems.
Coast stations will receive ship's AIS data and use same for VTS purposes. Other unintended uses are being found for AIS and it will undoubtably become a much more widespread system in the future. Current uses include forward of cargo data to futures markets, insurance company operating limit threshold management and even use by the American military for friendly fire computation, known as blue force. This technology is going to become much more far reaching than originally intended for collision avaidance and identification purposes. One useful idea said to available now is the coast stations ability to produce 'virtual buoys', where buoyage appears on screen but does not exist in reality. It will probably replace Navtex for local navigational information broadcasts. Imagine a local harbourmaster giving latest information on entry requirements
Each vessel has a unique identifyer which includes a country code.
The web has many sites showing AIS tracking aorund the globe.
This is marinetraffic.com
Further information can be obtained from the following links.
Useful Links
http://en.wikipedia.org/wiki/Automatic_Identification_System
Live AISdata feeds
http://www.aisgreece.com/liveshipdata/index.htm
http://olivecottage.homeip.net/
Country codes lookup
http://www.itu.int/cgi-bin/htsh/glad/cga_mids.sh?lng=E
MMSI Lookup
http://www.itu.int/cgi-bin/htsh/mars/ship_search.sh
Using AIS
The components required to recieve and view AIS data are as follows.
AIS receiver
Separate VHF antenna or antenna splitter
Suitable chart plotter or PC with serial input and AIS ready Navigation program (e.g.Maxsea 10.3.2.1)
It is possible to collect analogue audio from a VHF receiver and with suitable software decode into digital data from the PC sound card
What information does it provide?
Class A and B AIS provide different levels of information and frenquency of transmission.
Grib Files
The american weather service produces a global weather model twice each day from sensors around the globe. The resulting forecast model is called gridded binary. To obtain the part of the globe you require, you specify the area of interest, the resolution (30 miles, 60 miles, 120 miles) the frequency up to 120 hours, and type of information (wind, pressure, precipitation etc) as a line of code in an email message.
Grib files have no human input, and are considered by meteorologists as raw data. Ours and others experience have shown consitently that grib files are generally accurate for three days and are a very good source of moving weather pattern information. Gribs are therefore at their best when looking at longer pasages and not spot locations. Many peoples favourite weather sites use the GFS model which is Grib!!!!
Example
send gfs:46N,29N,10W,37E|0.5,0.5|6,12,18,24,36,48,72,84,96,108,120|PRESS,WIND
As a grib file is only weather data, a map or chart is required to display the data to make sense of it. There are two primary ways to do this. Either a dedicated Grib viewer or overlay the data on a chartplotter. For the navigator the charplotter mas several advantages. All the navigation data can be seen on one screen simultaneously and some packages will allow you to calculate optimum routing based on weather data. These data layers can be turned on and off as needed for clarity. Grib files are delivered in two formats. Either .grb or .bz2 can be read directly by most viwing applications. BZ2 is a more compressed form and hence smaller to transmit.
To obtain a grib file, send an email to query@saildocs.com with the text above in the main body as shown below (outlook express)
Within a few seconds a reply with an attachment will be recieved. Save the attachment in a folder (e.g.Grib) Open your chosen grib viewer and then open the grib file. remember the forecast is for several days so your viewer application will be able to scroll through the forecast period. As grib fils are in a common format it is quite possible to open for instance a Saildocs grib in the Grib.US (Ugrib) application
The above grib file displayed in Airmail 3
the same grib file displayed in Maxsea 10.3.2.1
The files are available from a variety of sources, but not directly from the AWS. If you subscribe and pay, many different types of information is available, including water temperature and wave height. The standard Wind speed, direction, and barometric pressure is availale free of charge from different sources, the most well known is Saildocs, Mailasail. Grib.US's service includes precipitation using their own application interface, which is simple and ideal where any connection cost is based on volume not time.
Note: I have been told today that it is possible to download files directly from the Grib.Us site (for those experiencing problems at Yat Marin) but when I tried it crashed!!!
I would still maintain although it requires a little more preparation initially, the most flexible approach for 'bandwidth and/or cash impaired' users is sailmal.
The most accesible viewer is the one supplied to Sailmail and WinLink users. Airmail3 and the integrated ViewFax is a free download at www.siriuscyber.net/sailmail/ This new version is still a beta (pre release), but seems stable and importantly is Vista friendly
For complete information on recieving of gribs from saildocs send a blank email to info@saildocs.com , from mailasail go to www.mailasail.com .
A large amount of resource on these subjects is available on the web, of particular note, Frank Singleton is well known in the UK as both metorologist and yachtsman. He has extensive weather information on his site in a simple no nonsense format.
www.myweb.tiscali.co.uk/franksweather/
This page http://cruiseryachtnadine.blogspot.com/
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