Glossary of ECDIS related terms

Committee on Exchange of Digital Data CEDD Committee of the IHO responsible for the Transfer Standard for Digital Hydrographic Data until 1995.. The use of data set descriptive records i

of ECDIS-RELATED TERMS

3rd Edition - December 1997

Special Publication No 52Appendix 3

Published by the International Hydrographic Bureau

MONACO

of ECDIS-RELATED TERMS

3rd Edition - December 1997

Special Publication No 52Appendix 3

Published by theInternational Hydrographic Bureau

4, Quai Antoine 1erB.P 445 - MC 98011 MONACO Cedex

Principauté de MonacoTelex: 479 164 MC- INHORGTelefax: (377) 93 10 81 40E-mail: info@ihb.mcWeb: www.iho.shom.fr

The purpose of this Glossary of ECDIS-related terms is to facilitate reading and interpreting thestandards and specifications related to ECDIS issued by IMO and IHO, namely the ECDIS PerformanceStandards, the IHO Special Publications S-52 (including its Appendices) and S-57

This 3rd edition has been developed by the Glossary Working Group of the IHO Committee onHydrographic Requirements for Information Systems (CHRIS) It has been completely revised based on thelatest editions of the relevant ECDIS-related standards and specifications

The reader should be aware that it is not intended to cover everything that has a bearing on ECDIS,and that many definitions only reflect a rather narrow meaning the terms have in conjunction with ECDIS.The Glossary, therefore, should not be used as general reference for hydrographic, navigational orinformation technology terms Some of the relevant IHO specifications contain a glossary of terms on theirown Only those definitions which have a wider use beyond the limits of a particular publication have beenincorporated from these specific glossaries

The "invention" of new definitions has been avoided as far as possible Use has been made instead

of either general dictionaries such as the Hydrographic Dictionary (IHO Special Publication S-32), andBowditch, or of other relevant documents References are provided in square brackets It should be notedthat sometimes a definition taken from another source may be an excerpt from the original definition, or isslightly modified in order to better meet ECDIS terminology Where it was felt, however, that the specialmeaning of a term in conjunction with ECDIS requires a correspondingly specialized approach, newdefinitions were developed

Advantage has been taken of guidelines provided in the "Short guide for writing definitions"published by the ISO TC211 Committee [ISO] In particular, an attempt has been made to separate thecore of the definition from any additional explanations, examples etc through the addition of Notes

All entries to the Glossary are given in lower case, except acronyms and proper names Cross

references to other definitions in the Glossary are provided by italicizing the respective term Acronyms are

integrated in the Glossary with cross references Some illustrations are annexed to the Glossary to showrelationships between terms

Any suggestions for improvement, corrections and extensions are welcome As the Working Groupwill be disbanded on publication of this edition, comments should be addressed to the Chairman of CHRISthrough the International Hydrographic Bureau

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all other information

Term used in the Performance Standards for ECDIS to describe information not belonging to the

standard display Also sometimes called "on-demand information" (See Fig 3)

application profile

Data structure A defined subject of the S-57 [TS]

Note: An application profile is defined for a specific purpose, such as the transfer of ENC data.

applier

An entity controlling the application of the update information, e.g the mariner keying in update

information, or the software inside ECDIS automatically processing the ENC update information.[UG]

Specification Attributes are either qualitative or quantitative [TS]

Note: see Appendix A, IHO Object Catalogue.

attribute label/code

A fixed length numeric label or a 2-byte unsigned integer code of an attribute as defined in Appendix A, IHO Object Catalogue [TS]

attribute value

See attribute label/code.

Automatic Identification System (AIS)

An automatic communication and identification system intended to improve the safety ofnavigation by assisting in the efficient operation of vessel traffic services (VTS), ship reporting,ship-to-ship and ship-to-shore operations

Note: A transponder is an example of an AIS AIS information may be displayed on an ECDIS

automatic updating

Either the semi-automatic or the fully automatic means of updating the ENC/SENC [UG]

Automatic Radar Plotting Aid (ARPA)

A system wherein radar targets are automatically acquired and tracked and collision situationscomputer assessed and warnings given

S-57 conforming data at the data producer's site that does not contain any update records Once

this data is exchanged it becomes target data at the applier's site [TS]

Feature object which contains information about the cartographic representation (including text of

real world entities [TS]

Note: The ENC Product Specification prohibits the use of cartographic objects in ENCs.

cautionary note

Information calling special attention to some fact, usually a danger area shown on a chart, or otherpublication [HD]

cell

The basic unit for the distribution of ENC data covering a defined geographical area bounded by

two meridians and two parallels, the content of which must not exceed 5 Mbytes, and which is

intended for a particular navigational purpose.

chain

A sequence of one or more edges.

chain node

Data structure in which the geometry is described in terms of edges, isolated nodes and connected

nodes Edges and connected nodes are topologically linked Nodes are explicitly coded in the data structure (see Fig 5) [TS]

Note: Spatial objects may be shared between feature objects Where spatial objects are shared,

lines that cross are broken (into edges) at the intersection and a logical node is implied (ie nodesare not explicitly created, the geometry of the node remains part of the edge) Where spatial

objects are not shared, lines may cross without being broken at the intersection Areas are defined

by the sequence of edges that comprise their boundaries Lines are comprised of edges Point

feature objects may only reference isolated nodes.

chart amendment patch

A chart specifically designed to meet the requirements of marine navigation, showing depths of

water, nature of bottom, elevations, configuration and characteristics of coast, dangers and aids to

navigation [HD]

Note: The carriage of up-to-date charts (plus certain other nautical publications) by vessels at sea

is a mandatory requirement of SOLAS regulation V 20 The term nautical chart may be applied also to a specially compiled data base (e.g., the ENC), from which such a map can be displayed.

chart symbol

A character, letter, line style, or similar graphic representation used on a chart to indicate some

object, characteristic, etc [HD]

chartwork

All navigational procedures carried out on a chart, the elements and parameters of which are listed

in Annex 3 of the ECDIS Performance Standards.

CHRIS

See Committee on Hydrographic Requirements for Information Systems.

C.I.E colour system

Colour specification system established by the Commission Internationale de l'Eclairage, whichpermits a replicable description of any colour on any equipment; in contrast with other colourschemes, which are apparatus specific Colour is usually expressed in terms of the x and ychromaticity coordinates for the widely used chromaticity diagram, and a third dimension Yrepresenting the luminance (perceived as brightness) of the light in candela per square metre(cd/m2) C.I.E colour coordinates can be transformed into RGB coordinates of a calibrated CRT

clarifications section

One of the mechanisms used to maintain S-57 See maintenance document.

clutter

Excess information or noise data on a display reducing its readability.

Note: E.g., information overload on a chart, or confusing unwanted wave echoes on a radardisplay [HD]

coastal warning

A navigational warning promulgated by a national co-ordinator covering a coastal region or a

portion thereof

collection object

A feature object which describes the relationship between other objects [TS]

Note: An example of a collection object in S-57 is "aggregation" which is used, for example, to

group together the different objects which together constitute a Traffic Separation Scheme

colour calibration

In order to reproduce the IHO colours for ECDIS, a colour calibration at the monitor must be

performed to transform the CIE-specified colours for ECDIS into the colour coordinate system of the screen Calibration will ensure correct colour transfer at the time a display leaves the

manufacturer's plant Methods of colour maintenance under operational use are underinvestigation

Note: colour calibration is described in Appendix 2 of IHO S-52.

colour differentiation test diagrams

Screen diagrams supplied in the Presentation Library for use by the mariner to check brightness

and contrast settings and to find out whether the screen still has the capability of distinguishing theimportant colours

colour fill

Method of distinguishing different area features by filling areas with colour "Transparent" colourfill is used to allow information to show through the fill, e.g., soundings in a traffic separationzone

colour tables

Five colour tables are supplied in IHO S-52 Appendix 2, for selection by the mariner They are

bright sun, day white-background, day black-background, dusk and night

colours for ECDIS

The colours specified by the IHO for ECDIS have been developed by Perception Institutes to give

a clear display through the optimum colour contrast under all viewing conditions, and to minimiselight emission on the darkened bridge at night Colours are used to aid in distinguishing between

features Colours for ECDIS are specified in the CIE colour system.

Committee on ECDIS (COE)

Committee of the IHO responsible for ECDIS matters until 1995 Now replaced by the Committee

on Hydrographic Requirements for Information Systems (CHRIS).

Committee on Exchange of Digital Data (CEDD)

Committee of the IHO responsible for the Transfer Standard for Digital Hydrographic Data until

1995 Now replaced by the Committee on Hydrographic Requirements for Information Systems

(CHRIS).

Committee on Hydrographic Requirements for Information Systems (CHRIS)

A Committee of the IHO tasked with promoting and coordinating the development of officialdigital products and services

compilation

In cartography, the selection, assembly, and graphic presentation of all relevant informationrequired for the preparation of a new map/chart or a new edition thereof Such information may bederived from other maps/charts, aerial photographs, surveys, new data, and other sources

compilation scale

The scale at which the ENC data was compiled.

distribution Compilation update is implemented in S-57 by means of a re-issue of an ENC.

conditional symbology procedure

A decision-making procedure used to link an object-class to a symbol in cases where the symboldepends on circumstances (e.g whether a wreck is symbolised as an "isolated danger" depends on

its relationship to the safety contour chosen by the mariner), or where symbolisation is complex

(e.g light sectors)

course made good (CMG)

The single resultant direction from a vessel's point of departure to its point of arrival at any giventime [Bowditch]

Note: Relates to each leg of the track

course over ground (COG)

The direction of a vessel's path actually followed, usually a somewhat irregular line [Bowditch]

course up display

The information is shown on the display (radar or ECDIS) with the direction of the vessel's course upward The display orientation is stabilized by means of the gyro until a new course direction is

fed in

Note: Course-up orientation avoids the disadvantages with the head-up display due to yawing or

other changes in heading

cumulative update

The collection of all sequential correction information which has been issued since the last new edition of the ENC or since the last official update applied to the SENC [UG]

The process of querying a point-symbol, line or area for further information from the data base

which is not represented by the symbol.

data dictionary

Conveys the meaning of entities and attributes, the relationship between entities and attributes and

the relationship between attribute and value domains

data model

A conceptual specification of the sets of components and the relationships among the components

pertaining to the specific phenomena defined by the model reality A data model is independent of

specific systems or data structures The S-57 data model defines real world entities as a combination of descriptive and spatial characteristics These characteristics are defined in terms of

feature objects and spatial objects and the relationship between them See Fig 4.

data quality indicator

Indication of reliability and accuracy of surveys of a particular area provided through CATZOC

attribute of the quality of data meta object in S-57.

data set

A logical grouping of S-57 data to which the S-57 data set descriptive records apply The data set descriptive records contain meta data The use of data set descriptive records is product specific and is, therefore, defined by a product specification If the data set descriptive records are repeated for each file in an exchange set, an instance of a file containing the data set descriptive records is

called a data set If the data set descriptive records are encoded generally for the whole exchangeset, the exchange set is referred to as a data set [TS]

For a local geodetic datum the reference surface is defined by five parameters: the latitude andlongitude of an initial point, the azimuth of a line from this point, and the parameters of thereference spheroid

Absolute datums specify the initial point of the reference ellipsoid to be (ideally) located at theearth's centre of mass For modern reference systems using datum information given by satellitesadditional parameters are defined, e.g gravity models [HD]

The deterioration in the performance of a system below a specified minimum level

Note: For example, the reduction in the information content of a display, a data base or othermeans of providing information below an acceptable or agreed level [IEC]

Differential GLONASS (DGLONASS)

see GLONASS

digital terrain model (DTM)

A model representing the terrain surface by a collection of digital data, mainly coordinates in threedimensions, x, y, and z, and a digitally defined method to interpolate arbitrary terrain heights inbetween the stored values [HD]

Note: Not to be confused with digital cartographic model which may also contain digital datarepresenting terrain, but in a form suitable for the drawing of a particular kind of map

digitizing conventions

see encoding conventions

display

A visual presentation of data

Note: For example, a presentation of a line of alphanumeric data, a window or the entire screen

display base

see display category

display category

The ECDIS Performance Standards establish three categories for SENC objects:

display base: permanently retained on the display

standard display: displayed at switch-on, recalled by single operator action

all other information: displayed individually (by class) on demand.

The category of every object is given in the look-up table See Fig 2, 3.

display generator

Software written by the ECDIS manufacturer to take an object from the SENC, assign a symbol and colour to it, and present it appropriately on the display, using the tools and procedures provided in the Presentation Library.

display priority

Detailed rules to decide which line or point symbol is to be shown when two objects overlap Priority 2 overwrites 1 Display priority is given in the look-up table.

display priority for radar

Radar is normally written over most chart areas and under most lines and point symbols; the detailed priorities are given in the look-up table.

display priority layer

Layers to establish the priority of information on the display Information of lower priority must

not obscure higher priority information

Note: Specifies, within a display priority layer, which of two overlapping objects is drawn on top

A one-dimensional spatial object, located by two or more coordinate pairs (or two connected

nodes) and optional interpolation parameters If the parameters are missing, the interpolation is

defaulted to straight line segments between the coordinate pairs In the chain-node, planar graph and full topology data structures, an edge must reference a connected node at both ends and must not reference any other nodes [TS]

electronic chart

Very broad term to describe the data, the software, and the electronic system, capable of displaying

chart information An electronic chart may or may not be equivalent to the paper chart required by SOLAS.

Electronic Chart Data Base (ECDB)

The master data base for Electronic Navigational Chart Data (ENCD), held in digital form by the national hydrographic authority, containing chart information and other nautical and hydrographic

information (See Fig 1) [UG]

Electronic Chart Display and Information System (ECDIS)

A navigation information system which with adequate back-up arrangements can be accepted as complying with the up-to-date chart required by regulation V/20 of the 1974 SOLAS Convention,

by displaying selected information from a System Electronic Navigational Chart (SENC) with positional information from navigation sensors to assist the mariner in route planning and route

monitoring, and if required display additional navigation-related information [PS]

Electronic Chart Systems (ECS)

Generic term for equipment which displays chart data but which is not intended to comply with

the IMO Performance Standards for ECDIS, and is not intended to satisfy the SOLAS Chapter V

requirement to carry a navigational chart

Electronic Navigational Chart (ENC)

The data base, standardized as to content, structure and format, issued for use with ECDIS on theauthority of government authorized hydrographic offices The ENC contains all the chartinformation necessary for safe navigation and may contain supplementary information in addition

to that contained in the paper chart (eg sailing directions) which may be considered necessary forsafe navigation (See Fig 1, 2) [PS]

Electronic Navigational Chart Data (ENCD)

The national data for an Electronic Navigational Chart (ENC) in a format acceptable to an ENC

Coordinator (See Fig 1) [UG]

Note: The content, structure and format of the ENC are specified in IHO S-57 edition 3 and the associated ENC product specification [IEC].

Electronic Navigational Chart Data Base (ENCDB)

The master data base for production and maintenance of the ENC, compiled from national ENC

data (ENCD) (See Fig 1) [UG]

ENC

See Electronic Navigational Chart.

ENC cell structure

See cell.

ENC data

See Electronic Navigational Chart Data (ENCD).

ENC Product Specification

Appendix B1 of S-57 which specifies the content, structure and other mandatory aspects of an

ENC.

ENC test data set

A standardized data set supplied on behalf of the International Hydrographic Organization (IHO) that is necessary to accomplish all IEC testing requirements for ECDIS This data set is encoded according to the IHO S-57 ENC product specification and contains update information based on IHO S-52 Appendix 1 The specific requirements are listed in Annex F of IEC 61174.

encapsulation

The identification of fields and records and the grouping of fields and records and the data syntax

rules used

encoding conventions

A set of rules which must be followed when encoding data for a particular purpose

Note: For example, S-57 Appendix B1 lists the encoding conventions to be used when encoding

ENC data, such as the rules to be followed when encoding depth areas Sometimes referred to as

digitizing conventions

Enhanced Group Call (EGC)

A global automatic service by INMARSAT for addressing commercial messages (FleetNet) or

Maritime Safety Information (MSI) (SafetyNet) to groups or ships or all vessels in both fixed and

variable geographical areas Data transmission is based on INMARSAT Standard-C and takesplace at an effective transmission rate of 600 bit/s [UG]

The set of files representing a complete, single purpose (i.e product specific) data transfer The

ENC Product Specification defines an exchange set which contains one Catalogue file and at least

one data set file [TS]

extensions document

One of the three documents used to maintain S-57 It contains extensions, or other significant

changes to the Standard, which have been agreed by the appropriate IHO committee or workinggroup, and will be included in the next edition of the Standard

See also clarifications document, corrections document.

Note: Available from IHB only on demand [TS]

face

A two dimensional spatial object A face is a continuous area defined by a loop of one or more

edges which bound it A face may contain interior holes, defined by closing loops of edges These

interior boundaries must be within the outer boundary No boundary may cross itself or touch itself

other than at the beginning/end node None of the boundaries may touch or cross any other boundary Faces are defined only in the full topology data structure [TS]

feature

Representation of a real world phenomenon [ISO]

Note: For example, a particular cardinal buoy represented through a symbol on a chart

field

A named collection of labelled subfield(s) For example, IHO attribute label/code and IHO

attribute value are collected into a field named Feature Record Attribute.

file

An identified set of S-57 records collected together for a specific purpose The file content and structure must be defined by a product specification [TS]

fully automatic updating

The application of corrections to ENC data in the SENC in a fully integrated state, without human

intervention at the receiving end [UG]

full topology

A 2-dimensional data structure in which the geometry is described in terms of nodes, edges and

faces which are all topologically linked A planar graph with faces [TS]

generalization

The omission of less important detail when compiling a chart Its purpose is to avoid overloading

charts where space is limited [HD]

geo object

A feature object which carries the descriptive characteristics of a real world entity [TS] Note: The positional information is provided through the spatial object.

Geographic Information System (GIS)

A computer based system for handling and integrating data from a variety of sources which isdirectly or indirectly spatially referenced to Earth [HD]

geometric primitive

One of the three basic geometric units of representation: point, line and area (See Fig 4) [TS]

Global Maritime Distress and Safety System (GMDSS)

A global communications service based upon automated systems, both satellite based and

terrestrial, to provide distress alerting and promulgation of maritime safety information to

mariners [HD]

Note: This system has been developed by IMO through the SOLAS Convention.

Global Navigation Satellite System (GNSS)

A world-wide position, time and velocity radiodetermination system comprising space, ground and

user segments of which GPS and GLONASS are components [GNSS]

GLONASS (Global Navigation Satellite System)

A space-based, radio-positioning, navigation and time-transfer system operated by the Government

of the Russian Federation GLONASS to which differential corrections have been applied isknown as Differential GLONASS (DGLONASS)

GPS (Global Positioning System)

A space-based, radio-positioning, navigation and time-transfer system operated by the UnitedStates Government GPS to which differential corrections have been applied is known as

Differential GPS (DGPS).

ground stabilization

A display whereby own ship position is referenced to the ground Usually performed in

conjunction with radar/ARPA, it can be determined by computing set and drift or by the use of

GPS/differential GPS.

Harmonization Group on ECDIS (HGE)

Joint Working Group of IMO and IHO tasked with maintaining the ECDIS Performance

Standards and addressing other related issues.

heading (HDG)

The direction in which a vessel is pointed, expressed as an angular distance from north clockwisethrough 360 degrees A constantly changing value as a vessel yaws back and forth across thecourse due to the effects of sea, wind, etc [Bowditch]

IHO Transfer Standard for Digital Hydrographic Data

Originally published as SP57 (later S-57) Version 1 and then Version 2 The latest release of the standard, S-57 Edition 3, consists of a Theoretical Data Model, Data Structure, Object Catalogue,

ENC Product Specification, Use of the Object Catalogue for ENC and an Object Catalogue Data Dictionary Product Specification.

IHO test data set

See ENC test data set.

indication

See indicator.

indicator

Visual indication giving information about the condition of a system or equipment [PS]

information from other sources

Information contained within SENC not originating from HO's or the mariner.

Note: E.g., manufacturer's chart data of areas where no HO-information is available (See Fig 2,

See IHO INT 1.

International Electrotechnical Commission (IEC)

A worldwide non-governmental organization for standardization comprising all nationalelectrotechnical committees (IEC National Committees) The object of the IEC is to promoteinternational cooperation on all questions concerning standardization in the electrical andelectronic fields [IEC]

Note: Committee 80, Working Group 7 of IEC is responsible for developing the PerformanceRequirements for ECDIS to be published as document IEC 61174

International Hydrographic Organization (IHO)

Coordinates the activities of national hydrographic offices; promotes standards and providesadvice to developing countries in the fields of hydrographic surveying and production of nauticalcharts and publications [HD]

International Maritime Organization (IMO)

The specialized agency of the United Nations responsible for measures to improve the safety ofinternational shipping and to prevent marine pollution from ships [IMO]

ISO 8211

ISO standard on "Information processing -Specification for a data descriptive file for informationinterchange" This international standard specifies an interchange mechanism to facilitate the

transfer of files containing data records between computer systems It defines a generalizedstructure which can be used to transmit, between systems, records containing a wide variety ofdata types and structures It provides the means for the description of the contents of data recordsbut does not define the contents.

ISO 10646

This ISO standard specifies the Universal Multiple-Octet Coded Character Set (UCS) It isapplicable to the representation, transmission, interchange, processing, storage, input andpresentation of the written form of the languages (scripts) of the world as well as additionalsymbols

Note: used to represent certain national language character sets, for example Arabic and Chinese,

in S-57.

isolated node

An isolated zero-dimensional spatial object that represents the geometric location of a point

feature An isolated node is never used as a beginning or end node [TS]

Note: This publication is issued under the authority of a marine administration

List of Radio Signals

A publication tabulating and combining particulars of: coast radio stations, port radio stations,radio direction finding stations, radiobeacons, etc., as well as other information on radio servicesuseful to a navigator [HD]

Note: This publication is issued under the authority of a marine administration

local datum

Any geodetic datum defined for national purposes other than WGS84 which is adopted for usewith ECDIS