1.1  Introduction

This document describes an S-100 compliant product specification for a bathymetric surface product. Incorporating aspects of the navigation surface concept [Smith et al, 2002], an S-102 bathymetric surface product is a digital elevation model which represents the seafloor in a regular grid structure. It can be used alone or as an important element/source for future S-100 conformant ECDIS navigation. The product specification is based on the IHO S-100 framework specification and the ISO 19100 series of standards. It comprises the content model (spatial structure and metadata), encoding structure, portrayal and exchange file format for a bathymetric surface product.

1.2  References

[1]  S-100 edition 5.2.0: IHO Universal Hydrographic Data Model, International Hydrographic Organization (https://iho.int/uploads/user/pubs/standards/s-100/S-100_5.2.0_Final_Clean.pdf).

[2]  S-44 edition 6.1.0: IHO Standards for Hydrographic Surveys, International Hydrographic Organization (https://iho.int/uploads/user/pubs/standards/s-44/S-44_5E.pdf).

[3]  S-49 edition 2.1.0: STANDARDIZATION of MARINERS’ ROUTEING GUIDES, International Hydrographic Organization (https://iho.int/uploads/user/pubs/standards/s-49/S-49_Ed.2.1.0_Standardization%20of%20Mariners%20Routeing%20Guides_EN.pdf).

[4]  S-32 edition 1.0.0: Hydrographic Dictionary — Glossary of ECDIS Related Terms, International Hydrographic Organization (http://hd.iho.int/en/index.php/Main_Page).

[5]  ISO 8601:2004: Data elements and interchange formats — Information interchange — Representation of dates and times, International Organization for Standardization (https://www.iso.org/standard/40874.html).

[6]  ISO 639-2:1998: Codes for the representation of names of languages — Part 2: Alpha-3 code, International Organization for Standardization (https://www.iso.org/standard/4767.html).

[7]  ISO 19103:2015: Geographic information — Conceptual schema language, International Organization for Standardization (https://www.iso.org/standard/56734.html).

[8]  ISO 19111:2007: Geographic information — Spatial referencing by coordinates, International Organization for Standardization (https://www.iso.org/standard/41126.html).

[9]  ISO 19115-1:2014/Amd 1:2018: Geographic information — Metadata — Part 1: Fundamentals — Amendment 1, International Organization for Standardization (https://www.iso.org/standard/73118.html).

[10]  ISO 19115-2:2009: Geographic information — Metadata — Part 2: Extensions for imagery and gridded data, International Organization for Standardization (https://www.iso.org/standard/39229.html).

[11]  ISO/TS 19115-3:2016: Geographic information —  Metadata — Part 3: XML schema implementation for fundamental concepts, International Organization for Standardization (https://www.iso.org/standard/32579.html).

[12]  ISO 19123:2005: Geographic information — Schema for coverage geometry and functions, International Organization for Standardization (https://www.iso.org/standard/40121.html).

[13]  ISO/TS 19129:2009: Geographic information — Imagery, gridded and coverage data framework, International Organization for Standardization (https://www.iso.org/standard/43041.html).

[14]  ISO 19131:2007/Amd 1:2011: Geographic information — Data product specifications — Amendment 1: Requirements relating to the inclusion of an application schema and feature catalogue and the treatment of coverages in an application schema., International Organization for Standardization (https://www.iso.org/standard/51790.html).

[15]  ISO/IEC 19501:2005: Information technology — Open Distributed Processing — Unified Modeling Language (UML) Version 1.4.2, International Organization for Standardization and International Electrotechnical Commission (https://www.iso.org/standard/32620.html).

[16]  ISO 3166-2:2013: Codes for the representation of names of countries and their subdivisions — Part 2: Country subdivision code, International Organization for Standardization (https://www.iso.org/standard/63546.html).

[17]  ISO/TS 19130:2010: Geographic information — Imagery sensor models for geopositioning, International Organization for Standardization (https://www.iso.org/standard/51789.html).

[18]  ISO/TS 19130-2:2014: Geographic information — Imagery sensor models for geopositioning — Part 2: SAR, InSAR, lidar and sonar, International Organization for Standardization (https://www.iso.org/standard/56113.html).

[19]  ISO/TS 19139-1:2019: Geographic information — XML schema implementation — Part 1: Encoding rules, International Organization for Standardization (https://www.iso.org/standard/67253.html).

[20]  ISO/IEC 10646-1:2000: Information technology — Universal Multiple-Octet Coded Character Set (UCS) — Part 1: Architecture and Basic Multilingual Plane, International Organization for Standardization and International Electrotechnical Commission (https://www.iso.org/standard/29819.html).

[21]  The Navigation Surface: The Navigation Surface: A New Database Approach to Creating Multiple Products from High-Density Surveys, Smith S., Alexander L. and Armstrong A., International Hydrographic Review (http://scholars.unh.edu/ccom/976).

[22]  The Open Navigation Surface Project: The Open Navigation Surface Project, Calder B., Byrne S., Brennan R., Case J., Fabre D., Gallagher B., Ladner W., Moggert F. and Patron M., International Hydrographic Review (https://scholars.unh.edu/ccom/1011).

1.3  Terms, definitions and abbreviations

1.4  General S-102 data product description

1.5  Product Specification metadata

This information uniquely identifies this Product Specification and provides information about its creation and maintenance. For further information on dataset metadata, see Section 12.

1.6  IHO Product Specification Maintenance

4.1  Introduction

The Bathymetric Surface Product incorporates aspects of the Navigation Surface concept where in addition to estimation of depth, an optional estimate of the uncertainty associated with the depth can be computed and preserved. Figure 4-1 below shows a high-level overview of the structure of S-102. It shows that the Bathymetric Surface Product consists of a set of data comprising the HDF5 datasets plus a Digital Certification Block. The Digital Certification Block is mandatory so that the user can trace whether the data has been certified. The HDF5 file consists of metadata (spatial, feature and discovery) and collocated coverages consisting of depth and uncertainty values. S-102 uses the S-100 Data Protection Scheme to ensure certification and authentication.

Figure 4-1 — Overview Structure of S-102

Thus, the Bathymetric Surface Product is a hybrid of coverages, as defined in S-100, Part 8, and metadata packages as defined in S-100, Part 4. This is described in Clause 4.2.

4.2  Application Schema

The Application Schema Data Set Structure is shown in Figure 4-2 and Figure 4-3. They show a number of classes specialized for use in S-102 and two sets of implementation classes. An actual data set of S-102 bathymetry data only contains the implementation classes. All of the required attributes from the other classes in the application schema are satisfied by statements within the Product Specification. This approach to producing the Application Schema results in a very simple structure for implementation.

Figure 4-2 — Data Set Structure of S-102

The model in Figure 4-2 states that:

Figure 4-3 — Coverage Structure of S-102

The model in Figure 4-3 depicts the coverage type in this application schema:

4.2.1  Application Schema implementation classes

The implementation classes for the template application schema are shown in Figure 4-4. The attributes are shown for the coverage related classes together with the attribute classes.

In order to simplify the implementation, a number of defaults are assumed for S-102. These defaults simplify implementation and help simplify interaction with the Navigation Surface implementation from the Open Navigation Surface Working Group and other bathymetric gridded types. In the following sub clauses, the default values are emphasized so that they do not need to be encoded when generating an encoding of the implementation classes. However, if specified they must assume the stated values unless other options are stated.

Figure 4-4 — Implementation of Classes of S-102

4.2.1.1  Implementation classes description

4.2.1.1.1  BathymetryCoverage

4.2.1.1.1.1  BathymetryCoverage semantics

The class BathymetryCoverage has the attributes minimumDepth, maximumDepth, minimumUncertainty, and maximumUncertainty which bound the depth attribute and the uncertainty attribute from the S102_BathymetryValues record. BathymetryCoverage additionally contains the inherited attributes origin, offsetVectors, dimension, axisName, extent, sequenceRule, and startSequence from S100_Grid and CV_Grid.

The origin is a position in a specified coordinate reference system, and a set of offset vectors specify the direction and distance between the grid lines. It also contains the additional geometric characteristics of a rectified grid.

4.2.1.1.1.2  minimumDepth

The attribute minimumDepth has the value type Real and describes the lower bound of the depth estimate for all the depth values in S102_BathymetryValues record. This attribute is required. There is no default.

4.2.1.1.1.3  maximumDepth

The attribute maximumDepth has the value type Real and describes the upper bound of the depth estimate for all the depth values in S102_BathymetryValues record. This attribute is required. There is no default.

4.2.1.1.1.4  minimumUncertainty

The attribute minimumUncertainty has the value type Real and describes the lower bound of the uncertainty of the depth estimate for all the depth values in S102_BathymetryValues record. If all uncertainty values are populated with the fill value (i.e., if no actual uncertainties exist in the data), this attribute shall be populated with the fill value. This attribute is required. There is no default.

4.2.1.1.1.5  maximumUncertainty

The attribute maximumUncertainty has the value type Real and describes the upper bound of the uncertainty of the depth estimate for all the depth values in S102_BathymetryValues record. If all uncertainty values are populated with the fill value (i.e., if no actual uncertainties exist in the data), this attribute shall be populated with the fill value. This attribute is required. There is no default.

4.2.1.1.1.6  origin

The attribute origin has the value class DirectPosition which is a position that shall locate the origin of the rectified grid in the coordinate reference system. This attribute is required. There is no default. In the encoding this is split into properties gridOriginLatitude and gridOriginLongitude.

4.2.1.1.1.7  offsetVectors

The attribute offsetVectors has the value class Sequence<Vector> that shall be a sequence of offset vector elements that determine the grid spacing in each direction. The data type Vector is specified in ISO 19103:2015. This attribute is required. There is no default. The HDF5 encoding implements and simplifies offsetVectors in the form of two HDF5 attributes: gridSpacingLatitudinal and gridSpacingLongitudinal.

4.2.1.1.1.8  dimension

The attribute dimension has the value class Integer that shall identify the dimensionality of the grid. The value of the grid dimension in this product specification is 2. This value is fixed in this Product Specification and does not need to be encoded.

4.2.1.1.1.9  axisNames

The attribute axisNames has the value class Sequence<CharacterString> that shall be used to assign names to the grid axis. The grid axis names shall conform to those of the CRS. For the allowable CRS according to this specification, the axis names shall be “Latitude” and “Longitude” for unprojected data sets or “Northing” and “Easting” in a projected space.

4.2.1.1.1.10  extent

The attribute extent has the value class CV_GridEnvelope that shall contain the extent of the spatial domain of the coverage. It uses the value class CV_GridEnvelope which provides the grid coordinate values for the diametrically opposed corners of the grid. The default is that this value is derived from the bounding box for the data set or tile in a multi tile data set. In the encoding the property BoundingBox is used to hold the extent.

4.2.1.1.1.11  sequencingRule

The attribute sequencingRule has the value class CV_SequenceRule that shall describe how the grid points are ordered for association to the elements of the sequence values. The default value is “Linear”. No other options are allowed.

4.2.1.1.1.12  startSequence

The attribute startSequence has the value class CV_GridCoordinate that shall identify the grid point to be associated with the first record in the values sequence. The default value is the lower left corner of the grid. No other options are allowed.

4.2.1.1.2  S102_BathymetryValues

4.2.1.1.2.1  S102_BathymetryValues semantics

The class S102_BathymetryValues is related to BathymetryCoverage by a composition relationship in which an ordered sequence of depth values provide data values for each grid cell. The class S102_BathymetryValues inherits from S100_Grid.

4.2.1.1.2.2  values

The attribute values has the value type S102_BathymetryValueRecord which is a sequence of value items that shall assign values to the grid points. There are two attributes in the bathymetry value record, depth and uncertainty in the S102_BathymetryValues class.

4.2.1.1.3  DirectPosition

4.2.1.1.3.1  DirectPosition semantics

The class DirectPosition hold the coordinates for a position within some coordinate reference system.

4.2.1.1.3.2  coordinate

The attribute coordinate is a sequence of Numbers that hold the coordinate of this position in the specified reference system.

4.2.1.1.3.3  dimension

The attribute dimension is a derived attribute that describes the number of coordinate axes.

4.2.1.1.4  CV_GridEnvelope

4.2.1.1.4.1  CV_GridEnvelope semantics

The class CV_GridEnvelope provides the grid coordinate values for the diametrically opposed corners of an envelope that bounds a grid. It has two attributes.

4.2.1.1.4.2  low

The attribute low shall be the minimal coordinate values for all grid points within the envelope. For this specification this represents the Southwestern coordinate.

4.2.1.1.4.3  high

The attribute high shall be the maximal coordinate values for all grid points within the envelope. For this specification this represents the Northeastern coordinate.

4.2.1.1.5  CV_GridCoordinate

4.2.1.1.5.1  CV_GridCoordinate semantics

The class CV_GridCoordinate is a data type for holding the grid coordinates of a CV_GridPoint.

4.2.1.1.5.2  coordValues

The attribute coordValues has the value class Sequence<Integer> that shall hold one integer value for each dimension of the grid. The ordering of these coordinate values shall be the same as that of the elements of axisNames. The value of a single coordinate shall be the number of offsets from the origin of the grid in the direction of a specific axis.

4.2.1.1.6  CV_SequenceRule

4.2.1.1.6.1  CV_SequenceRule semantics

The class CV_SequenceRule contains information for mapping grid coordinates to a position within the sequence of records of feature attribute values. It has two attributes.

4.2.1.1.6.2  type

The attribute type shall identify the type of sequencing method that shall be used. A code list of scan types is provided in S-100, Part 10c. Only the value — linear shall be used in S-102, which describes scanning row by row by column.

4.2.1.1.6.3  scanDirection

The attribute scanDirection has the value class Sequence<CharacterString> a list of axis names that indicates the order in which grid points shall be mapped to position within the sequence of records of feature attribute values.

4.3  Feature Catalogue

4.4  Dataset types

4.4.2  Regular grid

4.4.2.1  S-102 coverages

The BathymetryCoverage contains depth and, optionally, uncertainty. The general structure of each is defined in S-100, Part 8 as a georectified grid.

The grid properties of origin and spacing are defined by attributes in the BathymetryCoverage.01 Feature Container Group. The grid is a two-dimensional matrix organized in row major order and starting from the southwestern-most data point. Thus, the first sample of the grid is the node at the southwest corner of the grid with location specified by the georeferencing parameters, the second is one grid resolution unit to the east of that position and at the same northing or latitude, and the third is two grid resolution units to the east and at the same northing or latitude. For $C$ columns in the grid, the $(C+1)$^th sample in the grid is located one grid resolution unit to the north but on the same easting or longitude as the first sample in the grid.

Figure 4-5 — S-102 Grid Node location

The two values, depth and uncertainty, are stored in the same grid as members of a data compound. The units of the depth values are in metres. The vertical distance is from a given water level to the bottom. Drying heights (drying soundings) are indicated by a negative depth value.

The reference vertical datum for the surface is one of the mandatory Metadata items. The unknown state for depth is defined to be 1,000,000.0 (1.0e6).

The uncertainty values are expressed as positive quantities at a node. As detailed in Table 10-8 and Table 10-9 the uncertainty grid supports multiple definitions of vertical uncertainty. This allows grids to span the expected range of data products from raw, full resolution grid to final compiled product. For example, a grid at the stage of final survey data processing should contain uncertainty information germane to the survey data itself and intended to be used for information compilation. A recipient of an S-102 file can refer to the uncertainty definition in the Metadata to gain an understanding of how the uncertainty was computed.

The undetermined state for uncertainty is defined to be 1,000,000.0 (1.0e6).

4.4.2.2  Extensions

In S-102 there are currently no extensions defined.

4.5  Multiple datasets

In order to facilitate the efficient processing of S-102 data, the geographic coverage of a given maximum display Scale may be split into multiple datasets.

4.6  Dataset rules

Each S-102 dataset must only have a single extent as it is a coverage feature.

There should be no overlapping data of the same maximum display scale, except at the agreed adjoining limits. Where it is difficult to achieve a perfect join, a buffer to be agreed upon by the producing agencies may be used.

4.7  Geometry

S-102 regular gridded coverages are an implementation of S-100 Grid Coverage (Part 8 — Imagery and Gridded Data).

5.1  Introduction

The geo-referencing for an S-102 Bathymetric Surface product shall be node-based, referenced from the southwestern-most node in a grid. Each sample in a grid represents the value in the grid at a point location at the coordinate specified, rather than an estimate over any area with respect to the coordinate. The reference position included in the metadata shall be given in the coordinates used for the grid and shall contain sufficient digits of precision to locate the grid with accuracy no worse than a decimetre on the surface of the ellipsoid of rotation of the chosen horizontal datum.

The Coordinate Reference System information contained in Table 5-1 is defined in the manner specified in S-100, Part 6. Note the vertical datum is defined through a second association role to a vertical reference system.

5.2  Horizontal Coordinate Reference System

Table 5-1 — S-102 Coordinate Reference Systems (EPSG Codes)

5.3  Vertical Coordinate Reference System

Although in this product there are no direct vertical coordinates the values of the depth attributes are indirectly such coordinates. Therefore, it is important to specify the vertical CRS to which these values conform. The vertical CRS is an earth gravity-based, one-axis coordinate system. The axis is oriented positive down.

The vertical datum must be taken from the code-list specified by the IHO Geospatial Information (GI) Registry for the attribute named Vertical Datum. It will be defined in the root element as an HDF5 attribute.

5.4  Temporal reference system

The temporal reference system is the Gregorian calendar for date and UTC for time. Time is measured by reference to Calendar dates and Clock time in accordance with ISO 8601:2004, Clause 5.4.4. A date-time variable will have the following 16-character format: yyyymmddThhmmssZ.

6.1  Completeness

6.2  Logical consistency

6.3  Positional accuracy

6.4  Temporal accuracy

Temporal accuracy, consistency, and validity of bathymetric grids are confined to elements of the vertical control processes. These aspects are addressed during the formulation and application of vertical control processes applied by the various hydrographic offices. Details of these processes will be included in the Lineage portion of the metadata defined in Section 12 of this Product Specification.

6.5  Thematic accuracy

7.1  Quality and source metadata

Quality and source metadata in S-102 are intended to enable and support future navigation software to appropriately auto-generate and attribute cartographic features such as custom depth contours and soundings from S-102 products, all while minimally impacting the overall file size of the product.

Quality and source metadata are encoded in a raster attribute table that is compliant with HDF-5 and S-100 and will provide valuable information about the bathymetry on a node-by-node basis compared to traditional vector-based metadata files, simplifying the interpretation and implementation by navigation software systems.

The fields of the feature attribute table are defined elsewhere in this Product Specification (Table 10-7).

Quality and source metadata in S-102 are based on S-101 quality attributes, with significant augmentations and omissions described below. The quality and source metadata support a three-fold purpose:

Quality and source metadata are encoded as records within a QualityOfSurvey information group, dataset featureAttributeTable (Table 10-7).

8.1  Maintenance and update frequency

Datasets are maintained by replacement on a dataset basis. That is, the entire data product and the associated metadata are replaced as a unit. This is unlike vector data that may be updated incrementally. Also, each replacement data set must have its own digital signature.

8.2  Data source

Data producers must use applicable sources to maintain and update data and provide a brief description of the sources that were used to produce the dataset.

8.3  Production process

Data Producers should follow their established production processes for maintaining and updating datasets.

9.1  Introduction

This clause describes the display of bathymetric surface data to support the safe navigation of marine vessels. The following portrayal options are intended to enhance mariner decision making while taking into consideration the need to minimize cluttering of the navigation display. S-102 portrayal options:

9.2  Generation and display of gridded bathymetry

Most modern hydrographic surveys are conducted using high-resolution multibeam sonar systems. While these systems provide a highly detailed depiction of the seafloor, the storage and processing requirements (that is, data management) can be challenging. A typical hydrographic survey can collect upwards of 10 billion depth estimates over a 30-day collection period.

Utilization of a gridded data structure eases the data management concerns of the hydrographer, providing the ability to safely reduce the total sum of collected depth estimates into a manageable quantity of representative nodal depths for processing and production. All gridded datasets should be exposed to rigid Quality Assurance/Control procedures to ensure the final gridded dataset accurately represents the real-world environment. Once a dataset passes an established Quality Assurance/Control process, modern chart production software is used to extract candidate nodal depths from the grid for consideration as final charted soundings.

Table 10-3 provides a listing of S-102 accepted gridding methods.

Annex F provides an example gridding process, discussing the difference between full-resolution source bathymetry, product scale grid, and charted sounding.

9.2.2  Use of sun-illumination

S-102 data can be visualized as a sun-illuminated or static (flat) dataset. The depiction of sun-illumination requires the entry of a sun azimuth and corresponding elevation. Figure 9-1 shows the difference between a sun-illuminated and static (flat) surface.

Informative values for sun azimuth angle and elevation have been provided in Table 9-1.

Table 9-1 — Sun Azimuth and Elevation Values

Attribute	Value in Degrees
	Sun-Illuminated	Flat Surface
Sun Azimuth Angle	315 Degrees	0.0 Degrees
Sun Elevation	45 Degrees	0.0 Degrees

Figure 9-1 — Sun-illuminated and Static (Flat) Shading

9.3  Generation and display of navigation zones

The addition of an S-102 dataset enhances the mariner’s ability to render and display, using colours, and higher resolution depth zoning directly from the grid.

At time of ingest a display system will delineate and display navigational depth zones by comparing the depth layer of the S-102 dataset to the mariner-defined vessel draft or default safety contour. Depth zone naming and colouring (Table 9-3 — Table 9-5, and Figure 9-2) may follow IHO S-52, Edition 6.1(.1).

Table 9-3 — Depth Zone and Colour Token Information for Day

Table 9-4 — Depth Zone and Colour Token Information for Dusk

Table 9-5 — Depth Zone and Colour Token Information for Night

Figure 9-2 — S-52, Edition 6.1(.1) Depth Zone Colouring for Day

10.1  Introduction

The S-102 data set must be encoded using the Hierarchical Data Format standard, Version 5 (HDF5).

The key idea behind the S-102 product structure is that each coverage is a feature. Each of these features is co-located with the others. Therefore, they share the same spatial metadata and each is required to correctly interpret the others.

For the use of HDF5, the following key concepts (S-100, Part 10c, Clause 5.1) are important:

In addition, datasets may be a compound (a single record consisting of an array of simple value types) and have multiple dimensions.

10.2  Product structure

The structure of the data product follows the form given in S-100, Part 10c — HDF5 Data Model and File Format. The general structure, which was designed for several S-100 products is given in Figure 10-1.

Figure 10-1 — Outline of the generic data file structure

Figure 10-1 shows the four levels defined within the HDF encoding as defined in S-100, Part 10c. Below is a further definition of these levels.

In Table 10-1 below, levels refer to HDF5 structuring (see S-100, Part 10c, Figure 9). Naming in each box below the header line is as follows: Generic name; S-100 or S-102 name, or nothing if none; and (HDF5 type) group, attribute or attribute list, or dataset. Figure 10-2 depicts the same structure using a graphical representation.

Table 10-1 — Overview of S-102 Data Product

Figure 10-2 — Hierarchy of S-102 Data Product

The following sections explain entries in Table 10-1 in greater detail.

11.1  Introduction

This clause describes how S-102 data will be delivered from the charting authority to the mariner.

11.2  Dataset

11.3  Exchange Set

The structure of an S-102 Exchange Set must be according to the structure described below, which is based on S-100, Part 17, Clause 17–4.2.

11.4  Exchange Catalogue

The Exchange Catalogue acts as the table of contents for the Exchange Set. The Catalogue file of the Exchange Set must be named CATALOG.XML. No other file in the Exchange Set may be named CATALOG.XML. The contents of the Exchange Catalogue are described in Section 12.

11.5  Data integrity and encryption

S-100 Part 15 defines the algorithms for compressing, encrypting and digitally signing datasets based on the S-100 Data Model. The individual Product Specifications provide details about which of the elements are being used and on which files in the dataset.

12.1  Introduction

The Metadata elements used in the Bathymetric Surface product are derived from S-100 and from ISO 19115-1:2014/Amd 1:2018 and ISO 19115-2:2009. Optionally additional metadata may be derived from ISO/TS 19130:2010 and ISO/TS 19130-2:2014 especially metadata relating to the sonar equipment which may have been used to acquire the bathymetric data.

S-102 metadata is encoded in two places:

12.2  Exchange Set metadata

For information exchange, there are several categories of metadata required: metadata about the overall Exchange Catalogue, metadata about each of the datasets contained in the Catalogue.

Figure 12-1 depicts the relationships of exchange set elements (datasets and feature/portrayal catalogues) and exchange set metadata. This figure is derived from Figure 17-2 in S-100 Edition 5.0.0 with relationships not applicable to S-102 omitted.

Figure 12-2 depicts the structure of the exchange catalogue and its component discovery metadata blocks. The structure is the same as in S-100, Part 17.

More detailed information about the various classes is shown in in Figure 12-3 and a textual description in Tables 12-1 to 12-16.

The discovery metadata classes have numerous attributes which enable important information about the datasets to be examined without the need to process the data, for example, decrypt, decompress, load, etc. Other Catalogues can be included in the Exchange Set in support of the datasets such as Feature and Portrayal.

Figure 12-1 — Components and associated metadata for the S-102 exchange set (S-100 5.0.0 Figure 17-2 with items not used by S-102 omitted)

Figure 12-2 — Relationship between exchange catalogue, discovery metadata, and dataset (from S-100 5.0.0 Figure 17-6)

Figure 12-3 — S-102 Exchange Set Class Details

The following clauses define the mandatory and optional metadata needed for S-102. In some cases, the metadata may be repeated in a national language. If this is the case it is noted in the Remarks column.

The XML schemas for S-102 exchange catalogues will be available from the IHO Geospatial Information (GI) Registry and/or the S-100 GitHub site (https://github.com/IHO-S100WG).

The S-102 exchange catalogue uses the S-100 exchange catalogue schemas which are available from the S-100 schema server at https://schemas.s100dev.net (downloadable archives are also available on the site for offline use). Implementation of the S-102-specific constraints described in clauses 12.X to 12.Y below is left to developer decision as it can be done in various ways depending on implementation frameworks and the requirements of production or application software.

12.3  Language

The exchange language must be English.

Character strings must be encoded using the character set defined in ISO/IEC 10646-1:2000, in Unicode Transformation Format-8 (UTF-8). A BOM (byte order mark) must not be used.

12.4  S102_ExchangeCatalogue

Each Exchange Set has a single S100_ExchangeCatalogue which contains meta information for the data in the Exchange Set.

S-102 uses S100_ExchangeCatalogue without extension. S-102 restricts certain attributes and roles as described in Table 12-1. These restrictions are in bold type and noted in the Remarks column.

Table 12-1 — S102_ExchangeCatalogue parameters

12.5  S100_DatasetDiscoveryMetadata

Dataset discovery metadata in S-102 restricts certain attributes and roles as described in Table 12-4. Optional S-100 attributes which are mandatory in S-102 are indicated in the Remarks column.

Table 12-4 — S100_DatasetDiscoveryMetadata parameters

12.6  MD_MaintenanceInformation

Table 12-12 — MD_MaintenanceInformation parameters

12.7  MD_MaintenanceFrequencyCode

S-100 (and therefore S-102) use a subset of the values allowed in ISO 19115-1.

Table 12-13 — MD_MaintenanceFrequencyCode parameters

12.8  S100_CatalogueDiscoveryMetadata

S-102 uses S100_CatalogueMetadata without modification.

Table 12-14 — S102_CatalogueMetadata parameters

12.9  Certificates and Digital Signatures

The classes S100_SE_CertificateContainer, S100_SE_DigitalSignatureReference, and S100_DigitalSignatureValue are defined in S-100, Part 15 and implemented in the S-100 generic schemas.

In accordance with S-100, Part 15, only the DSA algorithm is allowed from the S100_SE_DigitalSignatureReference enumeration.

S-102 uses S100_DigitalSignatureValue without modification. As stated in S-100, Part 15, Clause 15–8.11.4:

“The class S100_SE_DigitalSignatureValue is realized as one of either S100_SE_SignatureOnData (a digital signature of a particular identified resource) or an additional digital signature defined using the class S100_SE_AdditionalSignature, each of which is either a S100_SE_SignatureOnData or S100_SE_SignatureOnSignature element as described in clause 15-8.8. S-100 Part 17 metadata thus allows for multiple digital signatures, a single mandatory S100_SE_SignatureOnData and any number of additional signatures, either of the data or other signatures.”