Chart Terms

Basic Terms

Term Definition
electronic chart（ENC, Electronic Navigational Chart） A standardized dataset of navigational charts published by officially recognized hydrographic authorities, containing all essential information for safe navigation. May include supplementary information from paper charts critical for navigation safety.
Electronic Chart Display and Information System（ECDIS）

A computerized navigation system compliant with International Maritime Organization (IMO) regulations, integrating multiple automated functions and real-time information to replace traditional paper charts and enhance navigation safety and efficiency.
Inland Electronic Navigation Chart（IENC） A standardized digital representation of inland waterways featuring geographic elements, water depths, and navigation marks, structured in specified content and format.

Product Specifications

Term Definition
S-52 Electronic Chart Display and Information System Chart Content and Display Specifications Specifications established by the International Hydrographic Organization (IHO) defining chart content and display standards for ECDIS. Regulates symbolization, color schemes, and layer management to ensure consistent chart presentation across systems.
S-57 Digital Hydrographic Data Transfer Standard An IHO standard governing the format and structure for encoding, storing, and transmitting hydrographic data, particularly ENC datasets. Ensures global compatibility and interoperability of navigational chart data in ECDIS and other systems.
S-58 Electronic Chart Validation Standard An IHO specification providing technical validation rules to ensure ENC data compliance before release, enhancing chart reliability and safety through quality control checks.
S-98 Product Interoperability An IHO framework defining interoperability guidelines for S-100 series navigation products, including coordinated display, overlay, and priority settings between diverse maritime datasets.
S-100 Universal Hydrographic Data Model An IHO-developed flexible data framework supporting various marine applications like navigation, surveying, and meteorology. Provides standardized structures for modern electronic chart systems to achieve data interoperability.
S-101 Electronic Chart An IHO specification under S-100 series defining next-generation ENC formats and symbology. Replaces S-57 with enhanced visualization and functionality for modern navigation systems.
S-102 Bathymetric Surface An IHO standard specifying high-precision seabed terrain data formats for electronic navigation systems, typically using raster data to enhance safety in shallow waters and ports.
S-104 Water Level Information An IHO standard for encoding water level data to support voyage planning and real-time adjustments in tidal zones and shallow waters.
S-127 Maritime Traffic Management An IHO specification modeling maritime traffic features like separation zones and anchorages, ensuring consistent presentation across navigation systems.
S-131 Port Infrastructure An IHO standard guiding digital representation of port facilities including docks, anchorages, and navigation channels.
CJ-57 Inland Electronic Navigation Chart Technical Specifications Mandatory Chinese industry standard (JTS 195—3—2019) effective from August 15, 2019, administered by the Ministry of Transport. Specifies technical requirements for inland ENC production and usage.

Data Structures

Term Definition
*.000 file Standard file format for electronic chart data transmission.
Chart group A logical organizational structure managing multiple datasets within a chart to improve readability and management efficiency.
Exchange set A collection of files representing a complete data transfer package for a specific product purpose.
Feature Dataset A group of chart features corresponding to specific object codes and dataset types, uniquely identified by encoding and dataset category.
Feature Representation of real-world phenomena in electronic chart systems.
Attribute Characteristics of objects defined through specific codes, abbreviations, definitions, and allowable values.
Subfield The smallest informational unit within a field, containing specified data types and described by byte position and length.
Adjoining chart Adjacent chart sheets determined by chart subdivision rules.

Electronic Chart Display

Term Definition
Sounding point Depth measurement point indicating vertical distance from water surface to seabed. Displayed in ECDIS with integer values in larger fonts and decimal fractions in smaller fonts without decimal points.
Depth contour Lines connecting points of equal water depth to illustrate seabed topography, analogous to contour lines in terrestrial maps.
Depth area Zones color-coded by depth ranges for quick identification of underwater terrain variations.
Safety contour User-defined depth line in ECDIS, set deeper than vessel draft, highlighted for grounding alarms and safe navigation reference.
Shallow contour Boundary marking shallow zones. Areas between safety and shallow contours are light blue for conditional transit, while deeper blues indicate prohibited zones.
Deep contour Typically set at twice vessel draft, marking safe deep-water zones. Adjustable for purposes like anchorage depth.
Safety depth User-defined depth (vessel draft plus margin) emphasized in ECDIS displays for critical depth monitoring.

S-57

Term Definition
Object Identifiable information cluster associated with maritime features or navigational elements, containing attributes like position and type.
Feature Object Non-spatial representation of real-world entities with descriptive attributes.
Spatial Object Geometric representation of real-world entities containing positional data and optional attributes.
Meta Object Feature object describing common characteristics of other objects.
Extend Process of adding object types not originally defined in S-57 standard.
Record Data structure with tagged S-57 fields, uniquely identified by a key containing feature details.
Feature Record Encoded representation of feature objects categorized into geographic, meta, collection, and cartographic types.
Feature Object Identifier（FOID） Unique identifier combining producing agency (AGEN), feature ID number (FIDN), and subdivision (FIDS), also known as Long Name (LNAM) in S-57.
Feature Record Identifier（FRID） Unique ID for each feature record in S-57 datasets ensuring unambiguous reference.
Record Identifier（RCID） Unique numerical identifier for feature records within datasets.
Record Name（RCNM） Descriptive name associated with feature records.
Master-slave Dependency relationship where a master object governs associated slave objects.

S-101

Term Definition
Feature Abstraction of real-world phenomena, either as types or entities.
Feature Attribute Characteristics of a feature.
Complex Attribute Attribute containing subfields, as opposed to simple attributes without subfields.
Information Types Supplementary annotations on charts providing contextual explanations beyond geographic depictions.
Connective Tissue Associated features and attributes linked to a feature object.
Related Information Relationships between feature types describing complex geographic entities and interactions.
Aggregation Whole-part relationship where parts can exist independently from the aggregate.
Feature Catalogue XML-based S-101 component detailing feature types, information types, attributes, and relationships for geographic datasets.
Portrayal Catalogue Files defining visualization rules and symbols for geographic data presentation.
Maximum Display Scale Largest scale at which data remains legible; beyond this scale, data is considered overscaled.
Minimum Display Scale Smallest scale at which data remains appropriately visible.
Optimum Display Scale Ideal maximum scale for data presentation clarity.