S-57 IHO Transfer Standard for Digital Hydrographic Data

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Last update:	October 2020
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Scope & structure

S-57 describes the standard to be used for the exchange of digital hydrographic data between national hydrographic offices and for its distribution to manufacturers, mariners and other data users. For example, this standard is intended tobe used for the supply of data for ECDIS. This transfer and distribution has to take place in such a way that none of the meaning of the data is lost.

The contents of S-57 are structured as follows:

• Part 1 - provides a general introduction including a list of references and definitions of terms used in the rest of the Standard
• Part 2 - describes the theoretical data model on which the entire Standard is based
• Part 3 - defines the data structure or format that is used to implement the data model and defines the general rules for encoding data into that format
• Appendix A Object Catalogue - provides the official IHO-approved data schema that can be used within an exchange set to describe entities in the real world
• Appendix B Product Specifications - additional sets of rules applicable to specific applications

ISO/IEC 8211 encapsulation

S-57 uses the international standard ISO/IEC 8211 (“Specification for a data descriptive file for informationinterchange”) as a means of encapsulating data. The ISO/IEC 8211 standard provides a file-based mechanism for the transfer of data from one computer system to another, independent of make. In addition, it is independent of the medium used to establish such a transfer. It permits the transfer of data and also the description of how such data is organized.

Model introduction

S-57 is designed to permit the transfer of data describing real world entities that are of relevance to hydrography.

This hydrographic regime is considered to be geo-spatial. As a result, the model defines real-world entities as a combination of descriptive and spatial characteristics. Within the model these sets of characteristics are defined in terms of feature objects and spatial objects.

An object is defined as an identifiable set of information. An object may have attributes and may be related to other objects.

Feature objects contain descriptive attributes and do not contain any geometry. Spatial objects may have descriptive attributes and must contain geometry.

A feature object is located by a relationship to one or more spatial objects. A feature object may existwithout referencing a spatial object, but each spatial object must be referenced by a feature object.