ECDIS

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THE OPERATIONAL USE OF ELECTRONIC CHART DISPLAY AND

INFORMATION SYSTEMS (ECDIS)

LEGAL ASPECT AND REQUIREMENTS

1 Application and requirements

1.1 Ships constructed on or after 1 July 2002 shall be fitted with

navigational systems and equipment which will fulfill the requirements

prescribed in paragraphs 2.1 to 2.9.

1.2 Ships constructed before 1 July 2002 shall: · subject to the provisions of paragraphs 1.2.2 and 1.2.3, unless they comply fully with this regulation, continue to be fitted with equipment which fulfils the requirements prescribed in regulations V/11, V/12 and V/20 of the International Convention for the Safety of Life at Sea, 1974 in force prior to 1 July 2002;

· be fitted with the equipment or systems required in paragraph 2.1.6 not later than the first survey after 1 July 2002 at which time the radio direction-finding apparatus referred to in V/12(p) of the International Convention for the Safety of Life at Sea, 1974 in force prior to 1 July 2002 shall no longer be required; and 

· be fitted with the system required in paragraph 2.4 not later than the dates specified in paragraphs 2.4.2 and 2.4.3.

2. Ship borne navigational equipment and systems

 2.1 All ships irrespective of size shall have:

   1. a properly adjusted standard magnetic compass, or other means, independent of any power supply to determine the ship's heading and display the reading at the main steering position;   2. a pelorus or compass bearing device, or other means, independent of any power supply to take bearings over an arc of the horizon of 360°;  3. means of correcting heading and bearings to true at all times;

4. nautical charts and nautical publications to plan and display the ship's route for the intended voyage and to plot and monitor positions throughout the voyage; an electronic chart display and information system (ECDIS) may be accepted as meeting the chart carriage requirements of this subparagraph;

5. back-up arrangements to meet the functional requirements of

subparagraph .4, if this function is partly or fully fulfilled by electronic means ; 

6. receiver for a global navigation satellite system or a terrestrial radio navigation system, or other means, suitable for use at all times throughout the intended voyage to establish and update the ship's position automatic means;

7. if less than 150 gross tonnage and if practicable, a radar reflector, or other means, to enable detection by ships navigating by radar at both 9 and 3GHz;

 8. when the ship's bridge is totally enclosed and unless the Administration determines otherwise, a sound reception system, or other means, to enable the officer in charge of the navigational watch to hear sound signals and determine their direction;

9. a telephone, or other means, to communicate heading information to the emergency steering position, if provided. 

2.2 All ships of 150 gross tonnage and upwards and passenger ships irrespective of size shall, in addition to the requirements of paragraph 2.1, be fitted with:

a spare magnetic compass interchangeable with the magnetic compass, as referred to in paragraph 2.1.1, or other means to perform the function referred to in paragraph 2.1.1 by means of replacement or duplicate equipment;

a daylight signaling lamp, or other means to communicate by light during day and night using an energy source of electrical power not solely dependent upon the ship's power supply.

2.3 All ships of 300 gross tonnage and upwards and passenger ships irrespective of size shall, in addition to meeting the requirements of paragraph 2.2, be fitted with:

an echo sounding device, or other electronic means, to measure and display the available depth of water;

a 9 GHz radar, or other means to determine and display the range and bearing of radar transponders and of other surface craft, obstructions, buoys, shorelines and navigational marks to assist in navigation and in collision avoidance;

an electronic plotting aid, or other means, to plot electronically the range and bearing of targets to determine collision risk;

speed and distance measuring device, or other means, to indicate speed and distance through the water;

a properly adjusted transmitting heading device, or other means to transmit heading information for input to the equipment referred to in paragraphs 2.3.2. 2.3.3 and 2.4.

2.4 All ships of 300 gross tonnage and upwards engaged on international voyages and cargo ships of 500 gross tonnage and upwards not engaged on international voyages and passenger ships irrespective of size shall be fitted with an automatic identification system (AIS), as follows:

ships constructed on or after 1 July 2002; ships engaged on international voyages constructed before 1

July 2002: in the case of passenger ships, not later than 1 July 2003;  in the case of tankers, not later than the first survey for

safety equipment on or after 1 July 2003;   in the case of ships, other than passenger ships and tankers,

of 50,000 gross tonnage and upwards, not later than 1 July 2004;    

in the case of ships, other than passenger ships and tankers, of 10,000 gross tonnage and upwards but less than 50,000 gross tonnage, not later than 1 July 2005;

in the case of ships, other than passenger ships and tankers, of 3,000 gross tonnage and upwards but less than 10,000 gross tonnage, not later than 1 July 2006;

in the case of ships, other than passenger ships and tankers, of 300 gross tonnage and upwards but less than 3,000 gross tonnage, not later than 1 July 2007; and

ships not engaged on international voyages constructed before 1 July 2002, not later than 1 July 2008.

the Administration may exempt ships from the application of the requirements of this paragraph when such ships will be taken permanently out of service within two years after the implementation date specified in subparagraphs 2 and 3;

AIS shall: provide automatically to appropriately equipped shore

stations, other ships and aircraft information, including the ship's identity, type, position, course, speed, navigational status and other safety-related information;

receive automatically such information from similarly fitted ships;

monitor and track ships; and  exchange data with shore-based facilities;

The requirements of paragraph 2.4.5 shall not be applied to cases where international agreements, rules or standards provide for the protection of navigational information; and

AIS shall be operated taking into account the guidelines adopted by the Organization

2. 5 All ships of 500 gross tonnage and upwards shall, in addition to meeting the requirements of paragraph 2.3 with the exception of paragraphs 2.3.3 and 2.3.5, and the requirements of paragraph 2.4, have:

a gyro compass, or other means, to determine and display their heading by shipborne non-magnetic means and to transmit heading information for input to the equipment referred in paragraphs 2.3.2, 2.4 and 2.5.5;

a gyro compass heading repeater, or other means, to supply heading information visually at the emergency steering position if provided;

a gyro compass bearing repeater, or other means, to take bearings, over an arc of the horizon of 360°, using the gyro compass or other means referred to in subparagraph. 1. However ships less than 1,600 gross tonnage shall be fitted with such means as far as possible;

rudder, propeller, thrust, pitch and operational mode indicators, or other means to determine and display rudder angle, propeller revolutions, the force and direction of thrust and, if applicable, the force and direction of lateral thrust and the pitch and operational mode, all to be readable from the conning position; and

an automatic tracking aid, or other means, to plot automatically the range and bearing of other targets to determine collision risk.

2.6 On all ships of 500 gross tonnage and upwards, failure of one piece of equipment should not reduce the ship's ability to meet the requirements of paragraphs 2.1.1. 2.1.2 and 2.1.4.

2.7 All ships of 3000 gross tonnage and upwards shall, in addition to meeting the requirements of paragraph 2.5, have:

a 3 GHz radar or where considered appropriate by the Administration a second 9 GHz radar, or other means to determine and display the range and bearing of other surface craft, obstructions, buoys, shorelines and navigational marks to assist in navigation and in collision avoidance, which are functionally independent of those referred to in paragraph 2.3.2; and

a second automatic tracking aid, or other means to plot automatically the range and bearing of other targets to determine collision risk which are functionally independent of those referred to in paragraph 2.5.5.

2.8 All ships of 10,000 gross tonnage and upwards shall, in addition to meeting the requirements of paragraph 2.7 with the exception of paragraph 2.7.2, have:

an automatic radar plotting aid, or other, means, to plot automatically the range and bearing of at least 20 other targets, connected to a device to indicate speed and distance through the water, to determine collision risks and simulate a trial maneuver; 

a heading or track control system, or other means, to automatically control and keep to a heading and/or straight track.

2.9 All ships of 50,000 gross tonnage and upwards shall, in addition to meeting the requirements of paragraph 2.8, have:

a rate of turn indicator, or other means, to determine and display the rate of turn; and

a speed and distance measuring device, or other means, to indicate speed and distance over the ground in the forward and athwartships direction.

When other means are permitted under this regulation, such means must be approved by Administration in accordance with regulation 18.

The navigational equipment and systems referred to in this regulation shall be so installed, tested and maintained as to minimize malfunction. 

Navigational equipment and systems offering alternative modes of operation shall indicate the actual mode of use.

Integrated bridge systems shall be so arranged that failure of one sub-system is brought to immediate attention of the officer in charge of the navigational watch by audible and visual alarms, and does not cause failure to any other sub-system. In case of failure in one part of an integrated navigational system, it shall be possible to operate each other individual item of equipment or part of the system separately.

Resolution A.817 (19)

The Performance Standards for Electronic Chart Display and

Information

Systems states that:

ECDIS, with adequate back-up arrangements, may be accepted as complying with the up-to-date charts required by regulations V/20 of the 1974 SOLAS Convention.

PERFORMANCE STANDARDS FOR ELECTRONIC CHART DISPLAY

AND IFORMATION SYSTEMS

1. INTRODUCTION1.1 The primary function of the ECDIS is to contribute to safe

navigation.

1.2 ECDIS, with adequate back-arrangements, may be accepted as complying with the up-to-date chart required by regulation V/20 of the 1974 SOLAS Convention.

1.3 In addition to the general requirements for ship borne radio equipment forming part of the global maritime distress and safety systems (GMDSS) and the requirements for electronic navigational aids contained in IMO resolution A.694 (17),* ECDIS should meet the requirements of this performance standard.

1.4 ECDIS should be capable of displaying all chart information necessary for safe and efficient navigation originated by, and distributed on the authority of, government-authorized hydrographic officers.

1.5 ECDIS should facilitate simple and reliable updating of the electronic navigational charts.

1.6 ECDIS should have at least the same reliability and availability of presentation as the paper chart published by government-authorized hydrographic offices.

1.7 ECDIS should provide appropriate alarms or indications with respect to the information displayed or malfunction of the equipment (see appendix 5)

2. Principal types of electronic chart

Chart Data Base 

At the heart of any integrated bridge system lays an electronic chart. An electronic chart system meeting International Maritime Organization (IMO) specifications for complying with chart carrying requirements is an Electronic Chart Display and Information System (ECDIS). All other electronic charts are known as Electronic Chart System (ECS).

ECDIS – Defined by the IMO as the integrated bridge system that complies with the up-to-date chart carrying requirements of international law.

ENC – is the ship’s electronic chart database used in an ECDIs system.

- a subset of the Electronic Chart Database (ECDB), the digital chart database maintained by the national hydrographic authority.

The Vector and the Raster Chart

Raster Chart data – is a digitized “picture” of a chart. All data is in one layer and one format. The video display simply reproduces the picture from its digitized data file.

- It is difficult to change individual elements of the chart since they are not separated in the data file. This data files tend to be large, since a data point must be entered for every picture element (pixel) on the chart.

Vector Chart data – is organized into many separate files. It contains graphics program to produce certain symbols, lines, area colors, and other chart elements. The programmer can change individual elements in the file and tag elements with additional data.

Vector files are smaller and more versatile than raster files of the same area. The navigator can selectively display vector data, adjusting the display according to his needs.

 3 ECDIS Data

System electronic navigational chart (SENC)

– means a database resulting from the transformation of the ENC by ECDIS for appropriate use, updates to the ENC by appropriate means, and other data added by the mariner.

- It is this database that is actually accessed by ECDIS for the display generation and navigational functions, and is the equivalent to an up-to date paper chart. The SENC may also contain information from other sources.

ECDIS should be capable of displaying all SENC information.

SENC information available for display during route planning and route monitoring should be subdivided into three categories, display base, standard display, and all other information (see appendix 2).

ECDIS should present the standard displayed at any time by a single operator action.

When a chart is first displayed on ECDIS, it should provide the standard display at the largest scale available in the SENC for the displayed area.

It should be easy to add or remove information from the ECDIS display. It should not be possible to remove information contained in the display base.

It should be possible for the mariner to select a safety contour form the depth contours provided by the SENC. ENDIS should give the safety contour more emphasis than the other contours on the displayed base.

  It should be possible for the mariner to select a safety depth contours

provided by SENC. ECIDS should give the safety contour more emphasis than other contours on the display.

The ENC and all updates to I should be displayed without any degradation of their information content.

ECDIS should provide a means of ensuring that the ENC and all updates to it have been correctly loaded into the SENC.

The ENC data and updates to it should be clearly distinguishable from other displayed information, such as, for example that listed in appendix 3.

The enterprise production environment

The Nautical Information System (NIS) is an enterprise environment that consists of centralized data. Using the NIS workflow, all data is stored and maintained in a Central Data Repository (CDR), and individual ENC products are maintained in isolated databases. Geodatabase replication is the mechanism that ensures that the data in these two databases is synchronized. The supporting information that is used to generate the individual product databases, such as geographic area of interest and scale band definition, is stored in another database called the product library, which may or may not be a physically different database than the CDR.

Each product database is built on the ArcSDE geodatabase and managed

through the product library.

The NIS workflow is the suggested workflow when creating and

managing a large number of products. Here are just a few of the

advantages of using the NIS workflow:

S-57 based, product neutral Central Data Repository. The NIS leverages ArcSDE technology. Takes full advantage of the Product Library data management

capabilities.

The desktop production environments

  The desktop workflows are client driven where the data for a given

product is isolated, meaning it is not replicated to another database. When setting up the desktop workflow, the product library is used to load the schema via Implement Instance.

There are two desktop production environments that you can use, depending on your data compilation needs. If you need to create S-57 data from scratch, run the Populate process using the Nautical Desktop Populator method. This method can be set at the product class level within the product class properties. If you need to modify existing S-57 data, you can just implement your product instance and import the cell directly into the product geodatabase.

Your databases are managed through the product library. Scaled down enterprise editing through Desktop/Workgroup connection. All edits are performed on the same database.

About producing an ENC

  The Nautical Solution ENC production environment is performed in the

ArcSDE versioning environment, whether using the enterprise (NIS) or desktop workflow. There are two approaches for working with data your products data.

You can create a product and create new data for it. You can create a product and load existing data into it.

Steps for working with new or existing data

PROVISION AND UPDATING OF CHART INFORMATION

The chart information to be used in ECDIS should be the latest edition of that originated by a government authorized hydrographic office, and conform to IHO standards.

The contents of the SENC should be adequate and up-to-date for the intended voyage to comply with regulation V/20 of the 1974 SOLAS Convention.

It should not be possible to alter the contents of the ENC.

Updates should be stored separately from the ENC.

ECDIS should be capable of accepting official updates to the ENC data provided in conformity with IHO standards. These updates should be automatically applied to the SENC. By whatever means updates are received, the implementation procedure should not interfere with the display in use.

ECDIS should also be capable of accepting updates to the ENC data entered manually with simple means for verification prior to the final acceptance of the data. They would be distinguishable on the display from ENC information and its official updates and not affect display legibility.

ECDIS should keep a record of updates including time of application to the SENC.

ECDIS should allow the mariner to display updates in order to review their contents and to ascertain that they have been included in the SENC.

ECDIS Units

The following units of measure will appear on the EC-DIS chart display:

Position: Latitude and Longitude will be shown in degrees, minutes, and decimal minutes, normally based on WGS-84 datum.

Depth: Depth will be indicated in meters and decimeters. Fathoms and feet may be used as an interim measure only:

• When existing chart data is held in those units only,

• When there is an urgent need for an ENC of the applicable area, and

• Time does not allow for an immediate conversion of the English units to their metric equivalents.

Height: Meters (preferred) or feet.

Distance: Nautical miles and decimal miles, or meters. 

Speed: Knots and decimal knots.

4 Presentation of ECDIS data

The major rules for presentation contained in the presentation

library for ECDIS

The IHO Presentation library is annex A to the IHO “Colour and Symbol

Specifications” (C&SS), which is in turn appendix 2 to IHO S-52

“Specifications for chart Content and Display Aspects of ECDIS”.

The presentation library implements the display specification in the S-52

App.2 by decoding and symbolizing the SENC. It contains:

1. The ECDIs symbol library, excluding the Navigation Symbols to be found in IEC 61174 and IEC 62288 (10).

2. The ECDIS colour for day, dusk and night viewing;

3. look-up tables, with symbology instructions linking SENC objects to the appropriate colour and symbol and giving their IMO category, draw priority, priority over radar, and suggested viewing group.

4. conditional symbology procedure for: cases where symbolizing depends on circumstances, such as the

mariner’s choice of safety contour. cases where symbolizing is too complex to be define in a direct look-

up table

5. description of symbology instructions

6. mariner’s navigational objects, specified in the same format as chart objects for convenience in processing in ECDIS,

7. supplementary features such as the ECDIS Chart 1, colour differentiation test diagram, colour calibration software.

COLORS AND SYMBOLS

Colours and symbols should be used to represent SENC information The colours and symbols other than those mentioned above should be that use to

describe the navigational elements and parameters listed in appendix 3 and published by IEC.

SENC information, when displayed at the scale specified in the ENC, should use the specific size of symbols, figures and letters.

ECDIs should allow the mariner to select whether own ship is displayed in true scale or as a symbol.

Location for the ECDIS display

- Experience in sea test has shown that it is important to select an appropriate location for ECDIS. For example:

- the navigator should be able to see the display clearly, and to reach the controls, from his normal conning position,

- it is an advantage to locate radar and ECDIS side by side

- the face of the display should be shaded from direct sunlight, and the display should not be located where the viewer may find the sun directly behind it.

Displaying Text

The power of ECDIS lies in conveying operational information quickly, clearly

and comprehensively through a picture, a bird’s eye view of the ship and her

surroundings. text should be avoided on this graphical operational display

unless it is absolutely necessary, because it conveys limited and, since it has

to be written large to be readable, causes confusing clutter.

However, some text may be unavoidable, both on the operational display (e.g.

buoy numbers if there are required for VTS reporting) or on a separate text

display (e.g. course to steer, heading; alarms; tidal information; user

interaction to control the ECDIS, etc.)

SENC INFORMATION AVAILABLE FOR DISPLAY DURING

ROUTE PLANNIGN AND ROUTEMONITORING

1. Display base, permanently retained on the ECDIS display, consisting of:

coastline (high water) own ship’s safety contour, to be selected by the mariner; indication of isolated underwater dangers at depths of less than the safety

contour which lie within the safe waters defined by the safety contour; indication of isolated dangers which lie within the safe water defined by the

safety contour such as bridges, overhead wires, etc., including bouys and beacons, whether or not these are being used aids to navigation;

traffic routing systems; scale, range, orientation, and display mode; units of depth and height

2. Standard displayed when the chart is first displayed by ECDIS, consisting of:

display base drying base indication of fixed and floating aids to navigation boundaries of fairways, channels, etc. visual and radar conspicuous features prohibited and restricted areas chart scale boundaries indication of cautionary notes

3. All other information, displayed individually on demand, for example: spot soundings submarine cables and pipelines ferry routes details of all isolated dangers details of aids to navigation contents of cautinary notes ENC edition date geodetic datum magnetic variation graticule place names

Picture 1: Standard Display, day

Picture 2: Standard Display, nigh

It should always be possible to display the SENC in a “north-up” orientation. Other orientation is permitted.

ECDIS should provide for true-motion mode. Other modes are permitted. When true motion is in use, reset and generation of the neighboring area

should take place automatically at a distance from the border of the display determined by the mariner

SENSORS PERFORMANCE STANDARDS FOR AUTOMATIC RADAR PLOTTING AIDS (ARPAs)

Detection

Where a separate facility is provided for detection of targets, other than by the

radar observer, it should have a performance not inferior to that which could be

obtained by the use of the radar display.

Acquisition

Target acquisition may be manual or automatic for relative speeds up to 100 knots. However, there should always be a facility to provide for manual acquisition and cancellation: ARPA with automatic acquisition should have a facility to suppress acquisition in certain areas. On any range scale where acquisition is suppressed over a certain area, the area of acquisition should be defined and indicated on the display.

Automatic or manual acquisition should have a performance not inferior to

that which could be obtained by the user of the radar display.

Tracking

The ARPA should be able automatically to track, process, simultaneously

display and continuously update the information on at least 20 targets,

whether automatically or manually acquired.

If automatic acquisition is provided, description of the criteria of selection of

targets for tracking should be provided to the user. If the ARPA does not track

all targets visible on the display, targets which are being tracked should be

clearly indicated with the relevant symbol* on the display. The reliability of

tracking should not be less than those obtainable using manual recordings of

successive target positions obtained from the radar display.

The ARPA should continue to track an acquired target which is clearly

distinguishable on the display for 5 out of 10 consecutive scans, provided

the target is not subject to target swop.

The possibility of tracking errors, including target swop, should be

minimized by ARPA design. A qualitative description of the effects of error

sources on the automatic tracking and corresponding errors should be

provided to the user, including the effects of low signal-to-noise and low

signal-to-clutter ratios caused by sea returns, rain, snow, low clouds and

non-synchronous emissions.

Display

The display may be a separate or integral part of the ship's radar. However,

the ARPA display should include all the data required to be provided by a

radar display in accordance with the performance standards for

navigational radar equipment.

The design should be such that any malfunction of ARPA parts producing

data additional to information to be produced by the radar as required by

the performance standards for navigational equipment should not affect the

integrity of the basic radar presentation.

The ARPA facilities should be available on at least 3, 6 and 12 nautical mile range scales, and there should be a positive indication of the range scale in use. ARPA facilities may also be provided on other range scales permitted by resolution A.477 (XII) and, if provided, should comply with these standards.

The ARPA should be capable of operating with a relative motion display with "north-up" and "course-up" azimuth stabilization. In addition, the ARPA may also provide for a true motion display. If true motion is provided, the operator should be able to select or the display either true or relative motion. There should be a positive indication of the display mode and orientation in use.

The course and speed information generated by the ARPA for acquired

targets should be displayed in a vector or graphic form which clearly

indicates the target's predicted motion with relevant symbols*. In this

regard: an ARPA presenting predicted information in vector form only

should have the option of both true and relative vectors. There should be an indication of the vector mode selected and, if true vector mode is selected, the display should show whether it is sea or ground stabilized;

an ARPA which is capable of presenting target course and speed information in graphic form should also, on request, provide the target's true and/or relative vector;

vectors displayed should be time-adjustable;

a positive indication of the time-scale of the vector in use should be given; and

if stationary targets are being used for ground referencing, this fact should be indicated by the relevant symbol*. In this mode, relative vectors including those of the targets used for ground referencing should be displayed when requested

The ARPA information should not obscure the visibility of radar targets. The display of ARPA data should be under the control of the radar observer. It should be possible to cancel the display of unwanted ARPA data within 3s. Means should be provided to adjust independently the brilliance of the ARPA data and radar data, including complete extinction of the ARPA data.

The method of presentation should ensure that the ARPA data are clearly

visible in general to more than one observer in the conditions of light normally

experienced on the bridge of a ship by day and by night. Screening may be

provided to shade the display from sunlight but not to the extent that it will

impair the observer's ability to maintain a proper look-out. Facilities to adjust

the brightness should be provided.

Provisions should be made to obtain quickly the range and bearing of any

object which appears on the ARPA display.

Accuracy

The ARPA should provide accuracies not less than those given in 3.8.2 and

3.8.3 for the four scenarios defined in appendix 2. With the sensor errors

specified in appendix 3, the values given relate to the best possible manual

plotting performance under environmental conditions of ± 10 degrees of roll.

An ARPA should present within one minute of steady state tracking the

relative motion trend of target with the following accuracy values (95%

probability values).

Note 1: In steady state tracking both own and target ship follow straight

line course at constant speed.

Note 2: Probability values are the same as confidence levels.An ARPA should present within three minutes of steady state tracking

the motion of a target with the following accuracy values (95%

probability values).

When a tracked target, or own ship, has completed a maneuver, the system should present in a period of not more than 1 min an indication of the target's motion trend, and display within 3 min the target's predicted motion, in accordance with 3.4.6, 3.6, 3.8.2 and 3.8.3. In this context, a "maneuver of own ship" should be deemed to consist of an alteration of course of + 45? in 1 min.

The ARPA should be designed in such a manner that under the most favorable conditions of own ship's motion the error contribution from the ARPA should remain insignificant compared to the errors associated with the input sensors, for the scenarios of appendix 2.

SENSOR ERRORS

The accuracy figures quoted in 3.8 of these standards are based upon the

following sensor errors, and are appropriate to equipment complying with the performance standards for shipborne navigational equipment.

Note: s means "standard deviation".

Radar

Target glint (scintillation) (for 200 m length target)

Along length of target s = 30 m (normal distribution)

Across beam of target s = 1 m (normal distribution)

Roll-pitch bearing: The bearing error will peak in each of the four quadrants

around own ship for targets on relative bearings of 045? 135?, 225?and 315?,

and will be zero at relative bearings of 0?, 90?, 180? and 270?.

This error has a sinusoidal variation at twice the roll frequency.

For a 10? roll the mean error is 0.22? with a 0.22? peak sine wave

superimposed. 

Beam shape - assumed normal distribution giving bearing error with s = 0.05?

Pulse shape - assumed normal distribution giving range error with s = 20 m

Antenna backlash - assumed rectangular distribution giving bearing error + 0.05? maximum

Quantization 

Bearing - rectangular distribution + 0.1? maximum.

Range - rectangular distribution + 0.01 nautical miles maximum. 

Bearing encoder assumed to be running from a remote synchro giving bearing errors

with a normal distribution s = 0.03?.

Gyro-compass

Calibration error 0.5?.

Normal distribution about this with s = 0.12?.

Log

Calibration error 0.5 knots.

Normal distribution about this, 3s = 0.2 knots. 

RECOMMENDATION ON PERFORMANCE STANDARDS

FOR RADAR EQUIPMENT

Range performance

The operational requirement under normal propagation conditions, when the radar

antenna is mounted at a height of 15 meters above sea level, is that the equipment

should in the absence of clutter give a clear indication of:

1. Coastlines

At 20 Nautical miles when the ground rises to 60 meters.

At 7 nautical miles when the ground rises to 6 meters.

2. Surface Objects

At 7 nautical miles when the ground rises to 60 meters.

At 3 nautical miles a small vessel of 10 meters in length.

At 2 nautical miles an object such as a navigational buoy having an effective

echoing area of approximately 10 square meters.

Minimum Range

 The surface objects specified in 3.1.2 should be clearly displayed from a

minimum range of 50 meters up to a range of one nautical mile, without

changing the setting of controls other than the range selector.

Display

The equipment should without external magnification provide a relative

plan display in the head-up unstabilised mode with an effective diameter of

not less than:

1. 180 millimetres on ships of 500 tons gross tonnage and more but less than 1,600 tons gross tonnage;

2. 250 miliimetres on ships of 1,600 tons gross tonnage and more but less than 10,000 tons gross tonnage; 

3. 340 millimetres in the case of one display and 250 millimetres in the case of the other on ships of 10,000 tons gross tonnage and upwards

The equipment should provide one of the two following sets of range scales of

display: 

1. 1.5, 3, 6 , 12 and 24 nautical miles and one range scale of not less than 0.5 and not greater than 0.8 nautical miles; or

2. 1, 2, 4, 8, 16 and 32 nautical miles.

  Additional range scales may be provided.

The range scale displayed and the distance between range rings should be

clearly indicated at all times.

Range measurement Fixed electronic range rings should be provided for range

measurements as follows:

1. when range scales are provided in accordance with 3.3.2.1, on the range

scale of between 0.5 and 0.8nautical miles at least two range rings should be provided and on each of the other range scales six range rings should be provided, or

2. Where range scales are provided in accordance with 3.3.2.2, four range rings should be provided on each of the range scales.

A variable electronic range marker should be provided with a numeric readout of range.

The fixed range rings and the variable range marker should enable the range of an object to be measured with an error not exceeding 1.5 percent of the maximum range of the scale in use, or 70 meters, whichever is the greater.

It should be possible to vary the brilliance of the fixed range rings and the variable range marker and to remove them completely from the display.

HEADING INDICATOR

  The heading of the ship should be indicated by a line on the display with a

maximum error not greater than plus or minus 1 degree. The thickness of the displayed heading line should not be greater than 0.5 degrees.

  Provisions should be made to switch off heading indicator by a device which

cannot be left in the “heading marker off” position.

BEARING MEASUREMENT Provision should be made to obtain quickly the bearing of any

object whose echo appears on the display.

The means provided for obtaining bearings should been able the bearing of a target whose echo appears at the edge of the display to be measured with an accuracy of plus or minus 1 degree or better.

GET A BEARING

A bearing is a measurement of direction between two

points. Bearings are generally given in one of

two formats, an azimuth bearing or a quadrant bearing.

An azimuth bearing uses all 360° of a compass to indicate

direction. The compass is numbered clockwise with

north as 0°, east 90°, south 180°, and west 270°. So a

bearing of 42° would be northeast and a bearing of

200° would be southwest, and so on. For quadrant bearings the compass isdivided

into four sections, each containing 90°. The two quadrants in the northern half of

the compass are numbered from 0° to 90° away from north (clockwise in the east,

counterclockwise in the west). In the southern half of the compass, the two

quadrants are numbered away from south (counterclockwise in the east,

clockwise in the west).

Quadrant bearings are given in the format of N 40°E (northeast), S 26°W (southwest), etc. Whenever you measure a quadrant bearing, it should always be recorded with north or south listed first, followed by the number of degrees away from north or south, and the direction (east or west) away from north or south. In other words, you would never give a quadrant bearing as E 40°N or W 24°S.

Your compass may be an azimuth compass or it may be divided into quadrants. If you have an azimuth compass and are given a quadrant bearing, you’ll have to divide it into quadrants in your head, and the same goes for quadrant compasses if you are given an azimuth bearing.

Measuring a bearing

So, you’re in the field with your map at point A and want to get to point B…how do you accomplish this? The first thing you need to do is determine the bearing from point A to point B. There are two ways to go about this.

The easiest way, is to carry a protractor with you when you’re in the field. If you have a protractor with you, place it on the map so it is oriented parallel to a north-south gridline, with the center of the protractor on point A (or on a line drawn between points A and B). Once you have done this, you can simply read the bearing you need to go off of the protractor. If you don’t happen to have a protractor with you, you can determine the bearing you need using your compass.

To do this, place your compass on the map so that the edge of your compass

is oriented parallel to a north-south gridline and the center of your compass is

on the line between points A and B.

Now rotate the map and compass together until the north arrow on the compass points to 0° on the graduated circle.

You can then approximate the bearing you need by estimating where the line between A and B crosses the graduated circle. It is probably at about this point that, if you are using a Brunton compass (and some others as well), you are probably noticing that the ‘east’ label is on the wrong side of the compass (west of north).

Going From Point "A" to "B"

Once you’ve figured out what direction you want to go, you need to figure out how to

use your compass to get you there. In the example on the previous page, you

determined that the bearing between A and B is 21° (N 21°E).  All you have to do now

is walk a straight line from point A to point B at 21° and, after a little sweat, you’ll be

at your destination.

To orient yourself along this path, orient your compass so that the north arrow is

pointing at the bearing you want, but in the adjacent quadrant.  For example, we want

to head out at a bearing of 20° (N 20°E).  To do so, align the north end of the needle

with 340° (N 20°W).

When you do this, the front edge of your compass is pointing 20° in the

direction you want to go.

Now perhaps it is clearer why on some compasses the east and west labels appear to be on the wrong side of the compass. If the bearing you want is N 20°E and the labels are swapped, then when you line up with N 20°E as labeled on the compass, the compass is truly pointing toward N 20°W.

Most compasses have some sort of sighting system built into them to allow greater accuracy in determining where you want to go. If your compass has a sight (check your owner’s manual to see if it has one and, if so, learn how to use it), you will orient it the same way as described above, but you can look through the sight at the same time and find an object to walk toward.

By finding an object (such as a tree or large rock) that lies along your path you will have more freedom to go around obstacles (such as large gullies, streams, hills, etc.) without losing track of the direction your are travelling.  Once you reach the object you were headed for, sight in on another object along your path, repeating this

process until you arrives at point B.

DISCRIMINATION The equipment should be capable of displaying as separate indications on a

range scale of 2 nautical miles or less, two small similar targets at a range of between 50 percent and 100 percent of the range scale in use, and on the same azimuth, separated by not more than 50 meters in range.

The equipment should be capable of displaying as separate indications two small similar targets both situated at the same range between 50 percent and 100 percent of the 1.5 or 2 mile range scales, and separated by not more than 2.5 degrees in azimuth.

ROLL OR PITCH

The performance of the equipment should be such that when the ship is rolling or

pitching up to plus or minus 10 degrees performance requirements of 3.1 and 3.2

continue to be met

SCAN

The scan should be clockwise, continuous and automatic through 360 degrees of

azimuth. The scan should not be less than 12 revolutions per minute. The equipment

should operate satisfactorily in relative wind speed of up to 100 knots.

AZIMUTH STABILIZATION Means should be provided to enable the display to be stabilized in azimuth by

a transmitting compass. The equipment should be provided with a compass input

to enable it to be stabilized in azimuth. The accuracy of alignment with the compass

transmission should be within 0.5 degrees with a compass rotation rate of 2

revolutions per minute.

The equipment should operate satisfactorily in the unsterilized mode when the compass control is inoperative.

PERFORMANCE CHECK

Means should be available, while the equipment is used operationally, to

determine readily a significant drop in performance relative to a calibration

standard established at the time of installation, and to check the equipment

is correctly tuned in the absence of targets.

ANTI-CLUTTER DEVICES

Suitable means should be provided for the suppression of unwanted echoes from

the sea clutter, rain and other forms of precipitation, clouds and sandstorms. It

should be possible to adjust manually and continuously the anti-clutter controls.

The anti-clutter controls should be inoperative in fully anti-clockwise positions. In

addition, automatic anti-clutter controls may be provided; however, they must be

capable of being switched off.

OPERATION The equipment should be capable of being switch on and operated

from the display position.

  Operational controls should be accessible and easy to identify and

use. Where symbols are used they should comply with the recommendations of the Organizations on symbols for controls on marine navigational radar equipment.

After switching on from cold the equipment should become fully operational within 4 minutes.

  A standby condition should be provided from which the equipment

can be brought to an operational condition within 15 seconds.

INTERFERENCE

After installation and adjustment on board, the bearing accuracy as prescribed in

this Recommendation should be maintained without further adjustments

irrespective of the movement of the ship in the earth’s magnetic field.

SEA OR GROUND STABILIZATION (True motion display)

  Where sea or ground stabilization is provided the accuracy and discrimination

of the display should be at least equivalent to that required by this Recommendation.

  The motion of the trace origin should not, except under manual override

conditions, continue to a point beyond 75 percent of the radius of the display. Automatic resetting may be provided.

ANTENNA SYSTEM

The antenna system should be installed in such a manner that the design efficiency of the radar system is not substantially impaired.

OPERATION WITH RADAR BEACONS

All radars operating in the 3 centimeter band should be capable of operating in a horizontally polarized mode.

It should be possible to switch off those signal processing facilities which might prevent a radar beacon from being shown on the radar display.

PERFORMANCE STANDARD FOR DEVICES

TO INDICATE SPEED & DISTANCE

METHOD OF PRESENTATION

Speed information may be presented in digital form. Where a digital display is used, its incremental steps should not exceed 0.1 knots. Analogue displays should be graduated at least every 0.5 knots and be marked with figures at least every 5 knots. If the display can present the speed of the ship in other than the forward direction, the direction of movement should be indicated unambiguously.

Distance run information should be presented in digital form. The display should cover the range from 0 to not less than 9999.9 nautical miles and the incremental steps should not exceed 0.1 nautical miles. Where practicable, means should be provided for resetting readout to zero.

The display should be easily readable by day and by night. Means should be provided for feeding distance run information to

other equipment fitted on board, in this regard:

  when contact closure used, forward speed only should be

indicated. The information should be in the form of one contact (or the equivalent) for 0.005 nautical miles run; and

when serial digital interface is provided, the information on all speed and distance parameters, including direction, should be provided in the form of a serial stream of digital information conforming to the international protocol for a digital interface for marine equipment use.

If equipment is capable of being operated in either the “speed through the water” or “speed over the ground” mode, mode selection and mode indication should be provided.

  If the equipment has provision for indicating speeds other than on

a single fore and axis, then the forward and athwart speed through the water must be provided, and the forward and athwart speed over the ground may be provided as a switchable option. All such information should clearly indicate the direction, mode and validity status of the displayed information.

ACCURACY OF MEASUREMENT

  Errors in the indicted speed, when the ship is operating free from

shallow water effect and from the effects of wind, current and tide, should not exceed 2% of the speed of the ship, or 0.2 knots, whichever is greater.

Errors in the indicated distance run, when the ship is operating free from shallow water effect and from the effect of wind, current and tide, should not exceed 2% of the distance run by the ship in 1 h 0.2 nautical miles in each hour, whichever is greater.

If the accuracy of devices to indicate speed and distance run can be affected by certain conditions e.g.:

sea state and its effect water temperature salinity, sound velocity in water depth of water under keel heel trim of ship

ROLL AND PITCH The performance of the equipment should be such that it will meet

the requirements of these standards when the ship rolling up to + 10° and pitching up to + 5°.

RECOMMENDATION ON PERFORMANCE STANDARSD

FOR GYRO-COMPASSES

METHOD OF PRESENTATION

  The compass card should be graduated in equal intervals of one degree

or a fraction thereof, A numerical indication should be provided at least at every ten degrees, starting from 000° clockwise through 360°

ILLUMINATION

Fully adequate illumination should be provided to enable reading of scales at all times. facilities for dimming should be provide

ACCURACY

SETTLING OF EQUIPMENT

When switched on in accordance with the manufacturer’s instructions the compass should settle within six hours in latitudes of up to 60°.

The settle point error as defined in paragraph 2.5 at any heading at any latitude up to 60° should not exceed ±0.75 x secant latitude where heading indications of the compass should be taken as the mean of 10 readings at 20 minute intervals, and the root mean square value of the differences between individual heading indications and the mean should be less than 0.25° x secant latitude. The repeatability of settle point error from one run-up to another shall be within 0.25° x secant latitude.

PERFORMANCE UNDER OPERATIONAL CONDITIONS

When switched on in accordance with the manufacturer’s instructions, the compass should settle within six hours in latitudes of up to 60° when rolling and pitching with simple harmonic motion of any period between six and fifteen seconds, a maximum angle of 5°, and a maximum horizontal acceleration of 0.22m/s2

The repeatability of the settle point error of the master compass shall be within + 1° x secant latitude under the general conditions mentioned in paragraph 6.1 and 8 and including variations in magnetic field likely to be experience in the ship in which it is installed.

In latitudes of up to 60°

1. the residual steady state error, after correction for speed and course influences at a speed of twenty knots, shall exceed +0.25 x secant latitude.

Means should be incorporated for the protection of the equipment from excessive currents and voltages, transients and accidental reversal of power supply polarity.

2. the error due to a rapid alteration of speed of twenty knots should not exceed + 2°.

3. the error due to rapid alteration of course of 180° at a speed of twenty knots should not exceed + 3°.

4.  the transient and steady state errors due to the ship rolling, pitching and yawning with simple harmonic motion of any period between six and fifteen seconds, maximum angle of 20°, 10° and 5° respectively and maximum horizontal acceleration not exceeding 1m/s2, should not exceed 1° secant latitude.

The maximum divergence in reading between the master compass and repeaters under all operational conditions should not exceed +0.5°

Note: When compass is used for purposes other than steering and bearing, a higher

accuracy might be necessary. To ensure that the maximum error referred to in sub-

paragraph 5.2.3.4 is not exceed in practice, it will be necessary to pay particular

attention to the sitting of the master compass.

POWER SUPPLY

The equipment should be capable of operating continuously in accordance with the requirements of these recommendations in the presence of such variations of the power supply as are normally expected in a ship.

If a provision is made for operating the equipment from more than one

source of electrical energy, arrangements for rapidly changing from one

source of supply to the other should be incorporated.

INTERFERENCE

  All steps should be taken to eliminate as far as practicable the causes of,

and to suppress, electromagnetic interference between the gyro-compass and other equipment on board.

Mechanical noise from all units should be so limited as not to prejudice the hearing of sounds on which the safety of the ship might depend.

  Each unit of the equipment should be marked with the minimum safe

distances at which it may be mounted from a standard or a steering magnetic compass.

PERFORMANCE STANDARDS FOR SHIPBORNEGLOBAL POSITIONING SYSTEM

(GPS) RECEIVER EQUIPMENT

GPS RECEIVER EQUIPMENT

  The words “GPS” receiver equipment as use in these performance standards

includes all the components and units necessary for the system properly to perform its intended functions. The equipment should include the following minimum facilities.

antennas capable of receiving GPS signals

2. GPS receiver and processor

3. means of accessing the computed latitude/longitude position;

4. data control and interface;

5. position display and , if required, other forms of output

  The antenna design should be suitable for fitting a position on the ship which

ensures a clear view of the satellite constellation.

The GPS receiver equipment should:

1. be capable of receiving and processing the Standard Positioning Service (SPS) signals modified by Selective Availability (SA) and provide position information in latitude and longitude World geodetic System (WGS) 84 co-ordinates in degrees, minutes and thousandths of minutes and time of solution reference to UTC. Means may be provided for transforming the computed position based upon WGS 84 into data compatible with the datum of the navigational chart in use. Where this facility exists, the display should indicate that co-ordinate conversion is being performed, and should identify the co-ordinate system in which the position is expressed;

2. operate on the L1 signal and C/A code;

3. be provided with at least one output from which position information can be supplied to other equipment. The output of position information based upon WGS 84 should be in accordance with IEC Publication 1162.

4. have statistic accuracy such that the position of the antenna is determine to within 100m (95%) with horizontal dilution of precision (HDOP) ≤ 4 (or PDO ≤ 6).

5. have dynamic accuracy such that position of the ship determined to within 100m (95%) with horizontal dilution of precision (HDOP) ≤ 4 (or PDO ≤ 6) under the conditions of sea states and ship’s motion likely to be experienced in ships;

6. be capable of selecting automatically the appropriate satellite-transmitted signals for determining the ship’s position with the required accuracy and update rate;

7. be capable of acquiring satellite signals with input signals having carrier levels in the range of 130 dBm to 120 dBm. Once the satellite signals have been acquired, the equipment should continue to operate satisfactorily with satellite signals having carrier levels down to 133 dBm.

8. be capable of acquiring position to the required accuracy within 30 minutes when there is no valid almanac data;

9. be capable of acquiring position to the required accuracy within 5 min when there is valid almanac data;

10. be capable of re-acquiring position to the required accuracy within 5 min when the GPS signals are interrupted for a period of at least 24 h but there is no loss of power.

11 be capable of re-acquiring position to the required accuracy within 2 min when subjected to a power interruption of 60s.

12 generate and output a new position solution at least every 2 s ;

13. the minimum resolution of position, i.e. latitude and longitude, should be 0.001 minutes; and

14 have the facilities to process differential GPS (DGPS) data fed to it in accordance with the standards of Recommendations ITU-R M. 823 and the appropriate RTCM standard. When a GPS receiver is equipped with a differential receiver, performance standards for static and dynamic accuracies (3.4 and 3.5 above) should be 10m (95%).

PROTECTION Precautions should be taken to ensure that no permanent damage can

result from an accidental short circuit or grounding of the antenna or any of its input or output connections or any of the GPS receiver equipment inputs or outputs for duration of 5 min.

PERFORMANCE STANDARDS

FOR ECHO-SOUNDING EQUIPMENT

Range of depths

  Under normal propagation conditions the equipment should be

capable of measuring any clearance under the transducer between two meters and 400 meters.

Range scales

  The equipment should provide a minimum of two range scales one of

which, the deep range, should cover the whole range of depth, and the other, the shallow range, one tenth thereof.

  the scale of display should not be smaller than 2.5mm per meter depth on

the shallow range scale and 0.25 mm per meter depth on the depth range scale.

METHOD OF PRESENTATION

The primary presentation should be a graphical display which provides the immediate depth and a visible record of soundings. Other forms of display may be added but these should not affect the normal operation of the main display.

ILLUMINATION Fully adequate illumination should be provided to enable identification of controls and

facilitate reading of record and scales at all times. Facilities for dimming should be provided.

PULSE REPITITION RATE The rate should be not slower than 12 pulses per minute.

ACCURACY OF MEASUREMENT

Based on a sound speed in water of 1500 metres per second , the allowable tolerance on the

indicated depth should be:

Either

+ 1 meter on the shallow range scale

+ 5 meters on the deep range scale 

Or 

+ 5 percent of the indicated depth, whichever is the greater

ROLL AND PITCH

  The performance of the equipment should be such that it will meet the

requirements of this Recommendation when the ship is rolling + 100 and/or pitching + 50.

POWER SUPPLY

The equipment should be capable of operating in accordance with the requirements of this recommendation in the presence of such variations of the power as are normally expected in a vessel.

Means should be incorporated for the protection of the equipment from excessive currents and voltages, transients and accidental reversal of power supply polarity.

if provisions is made for operating the equipment from more than one source of electrical energy, arrangements for rapidly changing from one source of supply to the other should be incorporated.

  all reasonable and practicable steps should be taken to eliminate the

causes of, and to suppress, radio interference to other equipment on board.

Mechanical noise from all units should be so limited as not to prejudice the hearing of sounds on which the safety of the ship might depend.

Each unit of the equipment should be marked with the minimum safe distances of which it may be mounted from a standard or a steering magnetic compass.

6 Basic Navigational functions and settings

NAVIGATIONAL ELEMENTS AND PARAMETERS

1. Own ship Past track with time marks for primary track Past track with time marks for secondary track

2. Vector for course and speed made good

3. Variable range marker and/or electronic bearing line

4. Cursor

5. Event Dead reckoning position and time (DR) Estimated position and time (EP)

6. fix and time

7. Position line and time8. Transferred position line and time

Predicted tidal streams or current vector with effective time and strength (in box)

Actual tidal stream or current vector with effective time and strength (in box)9. Danger highlight10. Clearing line11. Planned course and speed to make good. Speed is shown in box12. Waypoint13. Distance to run14. Planned position with data and time15. Visual limits of light arc to show rising/dipping range16. Position and time of “wheel-over” 

7 Specific Functions for route planning

Route Planning

  It should be possible to carry out route planning including both

straight and curved segments.

8 Specific function for route monitoring

ECDIS should give an alarm if the ship, within a specified time set by the mariner, is going to cross the safety contour.

ECDIS should give an alarm or indication, as selected by the mariner, if the ship, with a specified time set by the mariner, is going to cross the boundary of a prohibited area or of a geographical area for which special conditions exist.

An alarm should be given when the specified limit for deviation from the planned route is exceeded.

The ship’s position should be derived from a continues positioning system of an accuracy consistent with the requirements of safe navigation. Whenever possible, a second independent positioning method of a different type should be provided; ECDIS should be capable of identifying discrepancies between the two systems.

ECDIS should provide an indication when the input from the position-fixing system is lost. ECDIS should also repeat, but only as an indication, any alarm or indication passed to it from a position-fixing system.

An alarm should be given by ECDIS if the ship, within a specified time or distance set by the mariner, is going to reach a critical point on the planned route.

The positioning system and the SENC should be on the same geodetic datum. ECDIS should give an alarm if this is not the case.

9 Updating

Displaying ECDIS updates

Automatic and semi-automatic updates: these should be displayed in the same manner as ENC information, using standard colors and symbols. 

Manual Updates: should be displayed in standard colors and symbols and distinguished as describe in the presentation Library, Part I, section 8.7.

The mariner should be able to display updates for review as follows:

For automatic updates: the manufacturer should provide a means of distinguishing these. One method suggested is to identify automatic updates temporarily in the manner as manual updates. The temporarily switch on/switch off of the identifiers would distinguish automatic from manual updates.

For manual updates: display all SENC information. The manual updates should be distinguishable as described in the presentation Library, Part 1, section 8.7. 

10 Display and function of other navigational information

Automatic track-keeping (if fitted)

Track-keeping control allows the ship to maintain its planned track; whereas course-keeping only ensures that the ship is pointing in the right direction. Wind and currents can, for example, move the ship sideways and off its track while the ship's heading remains unchanged.

  For a ship to operate an automatic track-keeping system, the autopilot

should be adaptive and able to perform turns automatically between track legs, using either pre-set turn radius or rate of turn values.

Turns are commenced at a wheel over position, only after the OOW has acknowledged the wheel over position alarm and is satisfied that it is safe to execute the turn.

If a malfunction occurs when track-keeping, the system should alarm and revert immediately to course-keeping mode.

If the malfunction occurs while the autopilot is on a track, the autopilot should continue to steer the pre-set course of that track. If the autopilot is performing a turn when the malfunction occurs, the autopilot should complete the turn at the pre-set turn value and take up the course of the next track.

An autopilot performing automatic track-keeping functions and its alarm outputs should always be closely monitored.

The ability of the autopilot closely to follow a planned track will depend upon the accuracy of the XTE information sent to the autopilot from the navigation system.

11 Errors of Displayed Data

Hydrographic data inaccuracy

  The displayed hydrographic data are not more reliable than the survey data on

which they are based. The displayed sensor data are not more reliable than the respective sensor

systems they originate from. Errors and inaccuracies in one subsystem may influence the performance of

other subsystems and potentially render the ECDIS useless.

Use of Electronic Position-Fixing Systems Care should be taken when using electronic position-fixing systems.

Watchkeepers need to understand the capabilities and limitations of the systems they are using and continually monitor and validate the information given.

Use of Electronic Position-Fixing Systems in Integrated Bridges

When position-fixing systems transmit data to other navigation systems, the integrity and quality of the data transmitted need to be safeguarded;

Techniques used should include: Using pre-set quality limits to monitor the fix quality of each

position-fixing system connected to the integrated bridge.

Comparing all positions to identify and reject any rogue positions or positions that are clearly incorrect.

Comparing electronic positions with the ship’s estimated position (EP) calculated using direct inputs from the log and gyro.

Checking the status of the data transmitted and ensuring that only valid data messages are used.

12 Errors of Interpretation Detection of misrepresentation of information

Knowledge of the limitations of the equipment and detection of

misrepresentation of information is essential for the safe use of ECDIS. The

following factors should be emphasized: performance standards of the equipment; radar data representation on an electronic chart, elimination of

discrepancy between the radar image and the electronic chart; possible projection discrepancies between an electronic and paper

charts; possible scale discrepancies (overscaling and underscaling) in

displaying an electronic

chart and its original scale; effects of using different reference systems for positioning; effects of using different horizontal and vertical datums; effects of the motion of the ship in a seaway; ECDIS limitations in raster chart display mode; potential errors in the display of:

the own ship's position; radar data and ARPA information; different geodetic co-ordinate systems; and

verification of the results of manual or automatic data correction: comparison of chart data and radar picture; and Checking the own ship's position by using the other

independent position fixing systems.

13 Status indications, indicators and alarms

The different kinds of alarms and indicators of ECDIS can be divided into three

groups:

nautical alarms which may appear during route planning (e.g. the planned route is crossing a safety contour) or during route monitoring (e.g. the ship will cross a safety contour);

sensor alarms and indicators in the case of a failure or breakdown of a sensor (e.g. position fixing receiver failure during passage monitoring);

data and chart alarms resulting from a change geodetic datum or overscale setting.

An indication is required if the mariner plans a route across the boundary of a prohibited area or of a geographical area for which special conditions exist.

ECDIS should give an alarm or indication, as selected by the mariner, if the ship, within a specified time set by the mariner, is going to cross the boundary of a prohibited area or of a geographical area for which special conditions exist.

ECDIS should provide an indication of whether:

1. the information is displayed at a larger scale than that contained in the ENC; or

2. own ship’s position is covered by an ENC at a larger scale than that provided by the display.

14 Documentation

The essentials of automatic voyage recording

ECDIS should store and be able to reproduce certain minimum elements required to construct the navigation and verify the official database used during the previous 12 hours. The following data should be recorded at one-minute intervals:

to ensure a record of own ship’s past track: time, position, heading and speed; and

to ensure a record of official data used: ENC source, edition, date, cell and update history.

In addition, ECDIS should record the complete track for the entire voyage, with time marks at intervals not exceeding 4 hours.

It should not be possible to manipulate or change the recorded information.

ECDIS should have the capability to preserve the record of the previous 12 hours and of the voyage track.

15 Integrity Monitoring

To monitor for correct working, the system may incorporate:

self-diagnostic test routines to monitor for correct operation of hardware, operating system and ECDIS kernel during booting and normal operation;

diagnostic routine which may be executed at the request of the operators, e.g. manual test of hardware, MMI and sensor data as well as visual test of chart data.

16. Back-up

Adequate back-up arrangements should be provided to ensure safe navigation in case of an ECDIS failure.

facilities enabling a safe take-over of the ECDIS functions should be provided in order to ensure that an ECDIS failure does not result in a critical situation.

A back-up arrangement should be provided facilitating means for safe navigation of the remaining part of the voyage in case of an ECDIS failure.

17 Risk of over-reliance on ECDIS

o A potential risk of improper functioning of the system and of data inaccuracy is inherent in the system.

o That the displayed hydrographic data are not more reliable than the survey data on which they are based that the respective sensor systems they originate from.

o That ECDIS is only a tool that supports the mariner in the performing of the navigational tasks.

o That errors/inaccuracies in one subsystems may influence the performance of other subsystems and potentially render the ECDIS useless perform a navigational watch which is not based on only one system assess.

Hydrographic data inaccuracy The displayed hydrographic data are not more reliable than the survey

data on which they are based. The displayed sensor data are not more reliable than the respective sensor

systems they originate from. Errors and inaccuracies in one subsystem may influence the performance

of other subsystems and potentially render the ECDIS useless.

Potential risk of human errors There is the need to keep a proper look-out and to perform periodical

checking, especially of the ship’s position, by ECDIS-independent methods.

With or without the use of ECDIS, all navigational activities have to comply with the basic principles and operational guidance for officers in charge of a navigational watch.