Chart work is the art of laying a safe course, fixing the position and reassuring that position, while steering the ship on that course. It’s an imperative job which every navigating officer should master. It is also one of the top-tier skills which decide the competency of a ship navigator.

As there is no margin for errors in chart plotting, deck officers must have the perfect knowledge of doing it the right way . Mentioned below are important points that must be considered while doing chart plotting to avoid errors and do the job more efficiently.

1. Scale of the Chart

The Scale of the chart is the first thing to check before commencing Chart work. The chart scale is given down below the name of the Chart. After taking a note of it, allow yourself to glance through the latitude and longitude graduations along the chart. Once you are familiarised with the scale, the chances to do a wrong plot is largely reduced.  The depth scale of the chart should be considered as well.

 2. Notes of the Chart

Once you are aware of the scales, read down the notes which is also found below the Chart name. Such notes contain every important information regarding the navigation through that particular area covered by the chart. The information will include any submarine or naval exercise areas, anchoring, fishing areas, traffic separation schemes, any additional information about wrecks, tidal information and also local regulations concerning navigation.

3. Chart Symbols

A thorough knowledge of Chart symbol is highly insisted. Without understanding the correct symbols and its meaning, the reliability of the chart work will be diminished and the chances of errors will be higher. Any out of ordinary symbols which normally one don’t come across should be noted and checked using Nautical Publication 5011 . While doing Chart plotting, it is a good practise to keep NP 5011 ready for reference.

4. Chart Corrections

It is the responsibility of the Second officer to keep all the charts corrected up-to date with all permanent and temporary corrections which are received weekly via Notices to Mariners. The permanent corrections are marked on chart using magenta ink and T&P corrections are marked using pencil. It is very important not to miss out these corrections while doing chart plotting. As far as practical, avoid plotting course lines near or above any corrections. T&P corrections are more likely to be missed out as they are marked using pencil and tends to fade out in time. It is also a good practise to check if the corrections are upto date, they are normally mentioned at the bottommost side of the chart.

5. GPS Positions

GPS positions can be plotted directly on to all new BA Charts as they remain in the WGS-84 Datum. GPS positions have an accuracy of around 50 meters.  Avoid plotting GPS positions when navigating in costal and restricted waters as such margins can dangerous. Also while navigating in shallow waters, and when mountains near-by, multi-path errors can take place and hence the accuracy of the position will be further compromised.

6. Radar Fixes

Radar fix is considered as the most reliable fix while navigating in coastal waters. Radar fixes are best when it is fixed using Radar conspicuous objects such as a Racon or Ramark. Racon and Ramark are indicated on the charts by a magenta circle and are easily identifiable on Radar too. It is recommended to notice them on charts and use for position plotting. While plotting course lines, marking out the Radar conspicuous objects which can be used for fixes will be helpful.

7. Visual Fixes

Visual fixes will also give reliable positions while navigating near land. They can be taken from lighthouses and other aids to navigation. The bearings from the objects can be obtained using azimuth ring. Such bearings should be quickly and carefully plotted on charts for best fixes. If 3 bearings are used, the position will be inside the resultant ‘cocked-hat’ .The bearings from objects right angles to each other gives the best visual fixes, in practise.

8. Position Circle and Position Line

Position Circle is a circle drawn from an object (as its centre) and its range from the own-ship as radius. Position Line is a line drawn from the object along its bearing from the ship, the ship’s position is known to be in that line. A fix can be obtained using two parameters. ie, two position lines/ two position circles/ one position line and one position circle. The more parameters the better will be the accuracy of the fix. Since the ranges obtained from Radar are accurate, 3 position circles can give best fixes in practise. When there is only one object available, it is possible to fix the position using the ‘running fix’ technique. While doing chart plotting, the navigator should be familiar with different fixing techniques and use them appropriate to the available resources.

Chart work is a skill of accuracy and precision. The safety of navigations depends upon the quality and reliability of chart plotting. Hence the navigators doing chart plotting should do it with utmost care and attention. A wrong course line or position can mislead the vessel and can probably make way to accidents. Over reliance on GPS are commonly seen onboard. GPS positions are best to be used in open seas and the officer of the watch (OOW) must be aware of the accuracy of such positions. Encouraging the use of other fixing techniques we had discussed above, will be promising to enhance the skill of the navigator.

We appreciate more points as comments, if we missed any.

8 Things to Consider While Doing Nautical Chart Plotting On Ships appeared first on Marine Insight - The Maritime Industry Guide

Whenever a new area is to be added to a chart or it has to represent an area different from the previous chart, or the depth units shown on previous charts have to be changed or if the scale on which a previous chart was made has to be renewed, then Admiralty publishes a New Chart.

However if there are major changes in a chart or large amount of data is to be inserted  for e.g. Insertion of a New Traffic Separation Scheme not present on the previously used chart, the Admiralty then publishes a New Edition of that chart replacing the existing one.

The Catalogue of Admiralty Charts and Publications is published every year with current and updated editions of charts, however, if during the year the Weekly Notices to Mariner indicate any new editions or new charts, they are to be inserted in the chart catalogue by the navigating officer.

An updated and corrected chart folio system comprises of  Chart correction Log and Folio Index, Admiralty Chart catalogue, Admiralty Sailing Directions , Weekly Notices to Mariners , Annual Summary of Notices to Mariners,   Admiralty List of Lights , Admiralty List of Radio Signals , Admiralty Tide tables , Chart – 5011 Symbols and abbreviations to be used  on charts.  The following points to be considered in order to maintain updated chart folio onboard:

• The chart correction log should have details of all charts present onboard with index of corrections (temporary and preliminary also) mentioned against each chart number. All the charts and publications are to be corrected on weekly basis following instructions provided in weekly notices to mariners and the correction numbers to be entered in the same index mentioned above against chart numbers respectively, so that it can be used as a quick reference to check status of corrections for any chart
• There should be a designated chart supplier or service provided on a timely basis without delays to supply new charts and new editions applicable to the folios onboard. Other than that weekly Notice to mariners, Annual summary of Notices to Mariners, their supplements should be provided
• There should be equipment onboard and services to receive Navigational warnings, and Navtex warning

• Whenever a new chart or new edition is published, Weekly Notices to Mariner carry a notification of the same. On receiving a new edition or a new chart the chart correction log is to be updated with the relevant folio number against the chart number in the index and ‘NC’ or ‘NE’ to be inserted adjacent to the chart number in the correction index. The chart to be verified for any pending temporary and preliminary corrections and navigational warnings
• On receiving a chart or a notification through weekly notices to mariners which replaces a previous chart , insert in the chart correction log ‘replaced by’ or ‘cancelled by’ against the mentioned chart. The folio number to be inserted on the replacement chart received.

The Admiralty Chart Catalogue ( NP 131),Weekly Notices to Mariners , Cumulative Notices to Mariners and Annual summary of Admiralty Notices to mariners are important sources of keeping a Chart folio system updated and corrected. For guidance on correcting charts Admiralty has published – How to Correct Charts the Admiralty Way which describes various forms of corrections applied to charts and upkeep of folios. The importance of keeping charts updated can be understood from the below incident.

Real life incident: Due to negligence of a navigating officer a vessel was not allowed to enter a port for 2 days. After 2 days special permission was granted by USCG to the vessel upon request by the agents. The vessel did not have the latest edition of approach charts for the Port of Baltimore. The new edition had been published 4 weeks ago and vessel had received notification of the same. The USCG during their annual inspection pointed the error and the vessel was fined and allowed to berth after two days only when agents procured the new edition.                            

It is therefore important that during correcting charts the navigating officer has to exercise due diligence and care.                                                                              

Real Life Incident: Near Batu Berhanti Light in Singapore Straits a wreck is marked by 4 cardinal buoys surrounding it. During chart corrections the notice read as ‘Insert Isolated Danger Mark’ adjacent to the light. The duty officer misread it as ‘Delete’ and instead of inserting deleted the mark. The courses were laid from that area and while transit it was observed that the vessel passed very closed to the Isolated Danger Marks which were wrongly indicated on the chart.

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Fathom is a unit used to express feet. Fathom charts indicate depths in fathom and feet. They use a different style of color coding from metric charts though the symbols remains the same. For e.g. the land is shown in grey color on fathom charts.  Most of these charts were known to cover regions spread widely across the globe but gradually around 80 % of them have been phased out since 1998. Yet passing under bridges while approaching ports in the United States a navigator has to convert the maximum height of his ship in feet to ascertain safe clearance as the fathom charts are in use.

What replaced fathom charts then?

Post 1998 metric charts were introduced and a system was established to reproduce their updated editions and corrections in metric form only. They depicted depths in meters.  For representation of various features important to navigation different colors are used. For e. g. land is shown in yellow color, reefs in green color, Racon, Pilot station, and Traffic separation schemes in magenta color.

Reverting back to 1998, many trade routes and ocean passages through the major water bodies were covered by superimposing decca lattice on navigational charts and these charts were known as Decca Charts.

Similarly navigational charts superimposed with Loran – C lattice were known as Loran C Charts. For the ease of navigation on routes which have been frequented again and again over times by merchant ships, Admiralty came up with Routeing Charts. As the name suggests they provide vital information such as recommended seasonal tracks, distances between ports and bunkering ports, meteorological data, ice data, ocean currents, and load line zones at a glance. This information is available on a monthly basis as these charts are published for each month of the year.

Most of the navigational charts are based on Mercator projections. On these charts Equator and other parallels of latitude appear as horizontal parallel straight lines. For great circle sailing Gnomonic charts are being published so they can aid a navigator in determining shortest possible distance between 2 points. They cover the Atlantic, Pacific and Indian Ocean. Polar Regions too can be represented on gnomonic charts which otherwise can’t be on Mercator charts. For star identification and position fixing, Admiralty has also published Star charts and star diagrams. These charts used in conjunction with navigation formulae are used to take star sights, star identification and position fixing methods.

For busy traffic areas such as the Dover straits, Singapore and Malacca straits, Danish straits Admiralty has published Reference charts which represent the Traffic separation schemes and its constituents such as anchorages, precautionary zones, inshore traffic zones, radio reporting requirements and navigational warnings. These charts can be used as reference charts while planning passage through the areas they detail.

Admiralty has also introduced a digital representation of paper charts to be used with an electronic navigational system at sea. They are a digital representation of paper charts and are also known as Admiralty Raster Chart Service (ARCS), thus retaining the same clarity and accuracy.

An ECDIS electronic chart display and information system onboard can be set up in ARCS mode to use these charts. ENC stands for Electronic Navigational Charts which can be regarded as an intelligent navigation system database using internationally ratified symbols and format, in conjunction with a display and processing unit, can be used as an aid to navigation. Whenever this system complies with the requirements stated in SOLAS Regulation V/20 it can be used as an Electronic Chart Display and Information system (ECDIS) thus becoming equivalent to an up to date chart folio system.

Introduction to Nautical Charts – What Replaced Fathom Charts? appeared first on Marine Insight - The Maritime Industry Guide

Second mates on ships are often seen engrossed with drawing lines and working on those multi colored, thick bundles of sheets kept nicely stowed in canvass covers in various shelves in wheelhouse or Navigational Bridge.

Few have even wondered how a trivial task such as drawing courses on those sheets can make him so engrossed with his work. The fact is those conglomerations are popularly known as Charts and they happen to be the lifeline of ship navigation.

One cannot imagine navigation without charts. They are classified on the basis of the regions where they are printed, published, and updated or because of regional hydrographic offices controlling generation, assimilation and update of information concerning them.

The United Kingdom Hydrographic Office (UKHO) is the major organization dealing with upkeep of charts and numerous nautical publications. The Hydrographer of the Navy in United Kingdom is under the command of Admiralty – an administrative authority commanding the Royal Navy. Of their various functions one is to gather information in the form of hydrographic data, scrutinize it carefully, update it and broadcast the contemplated data in the form of paper charts, electronic charts and several allied publications.

A series of diagrammatic representation and index showing geographical limits of charts is provided in The Catalogue of Admiralty charts and Publications (NP 131). These publications have various regions of world into folios, which contain further detailed charts for those regions.

Broadly these charts are classified into two sections namely

• The large scale
• The small scale

These charts contain addresses of hydrographic offices and agencies where Admiralty and other charts are available.

Small scale charts                                                                                                         

Small scale charts shows overall details such as light vessels, light floats, lanbys, territorial waters and land separating adjoining countries, obstructions, shoals, reefs, buoys and fog signals .As the name suggests they represent a vast stretch of an area on a small scale thus representing macroscopic features of the same. For e.g. there are small scale charts for the Pacific ocean , South china sea , the Atlantic ocean , the Caribbean sea  etc. These charts are preferentially used as reference charts for planning routes and plotting courses, and from there on courses could be transferred to large scale charts. They are best suited to provide a general overview of passage.

Large scale charts                                                                                                         

Large scale charts are broader in terms of details and provide a much extensive representation of an area depicting the features, landmarks, harbors, and coastlines along with other important details. Differentiating fundamentally, the scale or the ratio of area displayed to actual area is considerably bigger than a small scale chart.

An area covered by a small scale chart can be split further into 10 , 20 or 30 large scale charts showing features such as full details and characteristics of principal lights and fog signals , light vessels , light houses , aids to navigations , leading lights , directional buoys , channel buoys , refineries , terminals , docks etc.  For e.g. on a small scale chart a principle lighthouse or light is marked with the help of a symbol whereas on a large scale chart along with the mark further details such as range, height, luminous range  and characteristics of the same are provided.

Though the UKHO covers expansive stretch of the ocean regions and ports, certain ports of the world remain uncovered by the Admiralty charts for those regions the local hydrographic offices prepare foreign charts using the internationally prevailing standard chart symbols and abbreviations. These charts also named as Foreign Charts are managed and kept updated using similar system to the Admiralty. They are usually available at national agencies at larger ports or designated hydrographic offices.

Another range of charts, which are also a part of Admiralty charts, are known as Australian and New Zealand Charts. These charts are kept updated by hydrographic offices located in New Zealand and Australia. Though published under the name of Admiralty they still carry their Australian and New Zealand Chart numbers. A comprehensive list for Australian and New Zealand charts can be obtained from the catalogues published by Australian and New Zealand hydrographic offices. They invariably cover regions surrounding Australia, New Zealand, Islands of Macquarie, and extend to Antarctica.

Japanese charts are also published by the Admiralty under similar arrangement. They too are being updated on the basis of information broadcasted by Japanese Hydrographic offices. However, the detailed list of charts in the Japanese folio can be found in the Admiralty chart catalogue and their corrections are provided in both Admiralty Notices to Mariners and Japanese charts as well.

There are two types of Japanese charts – One with Prefix ‘W’ and other with JP. For e.g. A chart printed as W 90 would contain information written in 2 languages – Japanese and English , the color of land is grey in this chart whereas a chart printed JP 90 would contain information in English only and color of land printed would be yellow. Japanese charts are available with British Admiralty and Japanese hydrographic offices as well.                                                                  

For Canadian and US waters as per the Code of Federal Regulations and Canadian charts and publications regulations, vessels navigating in certain specific regions are required to maintain and keep updated only Canadian and US charts.

Though being from different Hydrographic offices Charts have uniformity in the form of symbols and abbreviations, which have been recommended internationally and used globally, enabling mariners to plan passages using extensive information they require about distant ports across the oceans.

Introduction to Nautical Charts – Types of Navigation Charts Based on Origin appeared first on Marine Insight - The Maritime Industry Guide

As navigational maps have to aid ship’s captain and crew, nautical maps are drawn graphically with utmost precision. This process of map drawing is known as cartography. The information that is provided in nautical maps consists of the geography of a particular water area, the depth of the water in that area, the route navigating information and the level of tides and currents in that particular waters.

Information is also provided about the presence of any bridges or constructions in the water along with the deviations about the magnetic field of the Earth that tend to occur on water.

Nautical maps can be of two types:

• The traditional nautical charts drawn on paper
• The modern nautical maps that are created on computers (Digital or electronic maps)

In today’s times, most nautical maps are being created digitally with the help of computers. However, in case the electronic equipments fail, the traditional nautical charts are used simultaneously in order to avoid any unwanted problems that could arise in the absence of digital nautical maps.

Nautical maps are drawn on the basis of studies done on water areas. This is why sometimes it can so happen that there could be some errors on the chart. Such errors can be corrected appropriately but the usage of such error-filled charts should not be considered for future reference.

Also it is important that nautical charts are drawn and updated on a regular basis by the concerned authority. This will ensure that the captain of the ship will not have any problems when it comes to navigating the ship on tricky and unpredictable waters.

The extent of the area depicted depends on the size of a navigational chart. This means that if the size of the chart is bigger, the information about a larger water area can be shown which will benefit the captain of the ship. Smaller charts will reduce the water area depicted leading to a lot of unwanted complications for the ship’s captain.

There are different sources that offer nautical charts to seamen. Some well-known sources are TeamSurv, Marine GeoGarage and BlooSee. The navigational maps created by these sources are quite reliable and efficient.

Sea navigation is never perfect. The routes can be tracked completely but by using help like the nautical charts, the imperfect can be converted into being absolutely perfect.

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