2.1.  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.

2.2.  References

[1]  S-100 edition 5.0.0: IHO Universal Hydrographic Data Model, International Hydrographic Organization (https://iho.int/uploads/user/pubs/standards/s-100/S-100_5.0.0_Final_Clean_Web.pdf).

[2]  S-44 edition 5.0.0: 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 2.0.0: STANDARDIZATION of MARINERS’ ROUTEING GUIDES, International Hydrographic Organization (https://iho.int/uploads/user/pubs/standards/s-49/S-49_e2.0_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/TS 19103:2015: ISO and TS.

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

[9]  ISO 19115:2003: Geographic information — Metadata, International Organization for Standardization (https://www.iso.org/standard/26020.html).

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

[11]  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).

[12]  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).

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

[14]  ISO 19129:2009: ISO.

[15]  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).

[16]  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).

[17]  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).

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

[19]  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).

[20]  ISO/TS 19139:2007: Geographic information — Metadata — XML schema implementation, International Organization for Standardization (https://www.iso.org/standard/32557.html).

[21]  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).

[22]  IHO: The Navigation Surface: A New Database Approach to Creating Multiple Products from High-Density Surveys, Shep M. LT Smith, (http://scholars.unh.edu/ccom/976).

[23]  IHO: The Open Navigation Surface Project, Brian Calder, (https://scholars.unh.edu/ccom/1011).

2.3.  Terms, definitions and abbreviations

2.4.  General S-102 data product description

Title

Bathymetric Surface Product Specification

Abstract

This document is a Product Specification for a bathymetric surface which may be used alone or as an important element/source for future S-100 conformant ECDIS navigation. The product is defined as a data set with different coverages. This Product Specification includes a content model and separate encodings.

Acronym

S-102

Content

The Product Specification defines all requirements to which S-102 bathymetric data products must conform. Specifically, it defines the data product content in terms of features and attributes within the feature catalogue. The display of features is defined by the symbols and rule sets contained in the portrayal catalogue. The Data Classification and Encoding Guide (DCEG) provides guidance on how data product content must be captured. Annex A, in addition to Appendix 1, will provide implementation guidance for developers.

Spatial Extent

Description: Areas specific to marine navigation.
East Bounding Longitude: 180°
West Bounding Longitude: -180°
North Bounding Latitude: 90°
South Bounding Latitude: -90°

Purpose

The primary purpose of the Bathymetric Surface Product is to provide high resolution bathymetry in gridded form in support of safety of navigation. A Bathymetric Surface Product may exist anywhere in the maritime domain. There are no limitations to its extent. Portrayal of S-102 bathymetry with other S-100 compliant products are intended to support safe passage, precise berthing and mooring, as well as route planning of marine vessels. The secondary purpose of a bathymetric surface product is to provide high resolution bathymetric data for other maritime applications.

2.5.  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 Chapter 13.

Title

Bathymetric Surface Product Specification

S-100 Version

4.0.0

S-102 Version

2.1.0

Date

October 2022

Language

English

Classification

Unclassified

Contact

International Hydrographic Bureau
4 Quai Antoine 1er
B.P. 445
MC 98011 MONACO CEDEX
Telephone: +377 93 10 81 00
Fax: +377 93 10 81 40
Email: info@iho.int

URL

www.iho.int

Identifier

IHO:S100:S102:2:1:0

Maintenance

Changes to the Product Specification S-102 are coordinated by the IHO S-100 Working Group (S-100WG), and must be made available via the IHO web site. Maintenance of the Product Specification must conform to IHO Resolution 2/2007, as amended.

2.6.  IHO Product Specification Maintenance

5.1.  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 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 when the data product is produced for navigational purposes 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 1 — Overview Structure of S-102

Thus, the Bathymetric Surface Product is a hybrid of coverage(s), as defined in S-100, Part 8, and Information Types as defined in S-100, Part 4, together with a point set tracking list. This is described in Section 5.2.

5.2.  Application Schema

The Application Schema Data Set Structure is shown in Figure 2 and Figure 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 2 — Data Set Structure of S-102

The model in Figure 2 states that:

• An S-102 data set (S102_DataSet), which is inherited from S100_DataSet, references an S-102 Image and Gridded Data Collection (S102_IGCollection). In S-100 it is possible to have multiple collections but in S-102 only one is needed to hold the bathymetry coverage. The S-102 discovery metadata class (S102_DiscoveryMetadata) describes the metadata entities required for the identification of the entire data set. The required discovery metadata is implemented through the S102_DSMetadataBlock class.

• An instance of an S-102 Image and Gridded Data Collection (S102_IGCollection) which is a subtype of S100_IGCollection, is described by a set of S-102 Collection Metadata (S102_CollectionMetadata). This relationship is 1 to 1 meaning that there is one set of collection metadata for each instance of S102_IGCollection. There is a large choice of metadata that may be used in a S-100 compliant data product. Only a small amount of this metadata is mandated by ISO 19115:2003 for discovery. The choice of metadata is discussed in Section 13.2. Much of the metadata can be resolved as part of the product specification. Only that metadata that varies IG_collection item to item needs be included in the S102_MetadataBlock implementation class.

This is discussed further in Section 5.2.1.

Figure 3 — Coverage Structure of S-102

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

• The coverage type is a discrete Regular Grid Coverage called S102_DepthCoverage which inherits from (S100_GridCoverage). Many of the parameters of the coverage are described in the product specification.

5.2.1.  Application Schema implementation classes

The implementation classes for the template application schema are shown in Figure 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 — Implementation of Classes of S-102

5.2.1.1.  Implementation classes description

5.2.1.1.1.  BathymetryCoverage

5.2.1.1.1.1.  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.

5.2.1.1.1.2.  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.

5.2.1.1.1.3.  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.

5.2.1.1.1.4.  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.

5.2.1.1.1.5.  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.

5.2.1.1.1.6.  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.

5.2.1.1.1.7.  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/TS 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.

5.2.1.1.1.8.  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.

5.2.1.1.1.9.  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.

5.2.1.1.1.10.  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.

5.2.1.1.1.11.  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.

5.2.1.1.1.12.  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.

5.2.1.1.2.  S102_BathymetryValues

5.2.1.1.2.1.  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.

5.2.1.1.2.2.  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. The definition for the depth is defined by the depthCorrectionType attribute in the S102_DataIdentification class. The definition of the type of data in the values record is defined by the verticalUncertaintyType attribute in the S102_DataIdentification class.

5.2.1.1.3.  DirectPosition

5.2.1.1.3.1.  DirectPosition semantics

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

5.2.1.1.3.2.  coordinate

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

5.2.1.1.3.3.  dimension

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

5.2.1.1.4.  CV_GridEnvelope

5.2.1.1.4.1.  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.

5.2.1.1.4.2.  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.

5.2.1.1.4.3.  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.

5.2.1.1.5.  CV_GridCoordinate

5.2.1.1.5.1.  CV_GridCoordinate semantics

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

5.2.1.1.5.2.  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.

5.2.1.1.6.  CV_SequenceRule

5.2.1.1.6.1.  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.

5.2.1.1.6.2.  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 8. Only the value — linear shall be used in S-102, which describes scanning row by row by column.

5.2.1.1.6.3.  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.

5.3.  Feature Catalogue

5.4.  Dataset types

5.4.2.  Regular grid

5.4.2.1.  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 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 Section 13.2 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).

5.4.2.2.  Extensions

In S-102 there are currently no extensions defined.

5.5.  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.

5.6.  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.

5.7.  Geometry

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

6.1.  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 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.

6.2.  Horizontal Coordinate Reference System

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

Horizontal Coordinate Reference System

EPSG (see Table 1)

Projection

NONE/UTM/UPS

Temporal reference system

Gregorian Calendar

Coordinate Reference System registry

EPSG Geodetic Parameter Registry

Date type (according to ISO 19115:2003)

002 — publication

Responsible party

International Organisation of Oil and Gas Producers (OGP)

URL

http://www.ogp.org.uk/

6.3.  Vertical Coordinate Reference System

Although in this product there are no direct vertical coordinates the values of the depth attributes are indirect 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 defined by S100_VerticalAndSoundingDatum. It will be defined in the root element as an HDF5 attribute.

6.4.  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.

7.1.  Completeness

7.2.  Logical consistency

7.3.  Positional accuracy

7.4.  Temporal accuracy

7.5.  Thematic accuracy

9.1.  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. However, coverage data must be considered as a unit. Also, each replacement data set must have its own digital signature.

9.2.  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.

9.3.  Production process

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

10.1.  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:

• Display of gridded bathymetry

• Colouring options to support safe navigation.

10.2.  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 thirty-day collection period.

Utilization of a gridded data structure eases the data management concerns of the hydrographer, providing the ability to safely decimate 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.

Annex D 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.

10.2.2.  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 6 shows the difference between a sun-illuminated and static (flat) surface.

Informative values for sun azimuth angle and elevation have been provided in Table 2.

Table 2 — 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 6 — Sun-illuminated and Static (Flat) Shading

10.3.  Generation and display of navigation zones

The addition of S-102 dataset enhances the mariner’s ability to render and display, using colours, 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 4 — Table 6, and Figure 7) may follow IHO S-52, Edition 6.1(.1).

Table 4 — Depth Zone and Colour Token Information for Day

Table 5 — Depth Zone and Colour Token Information for Dusk

Table 6 — Depth Zone and Colour Token Information for Night

Figure 7 — S-52, Edition 6.1(.1) Depth Zone Colouring for Day

11.1.  Introduction

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

Format Name

HDF5

Version

1.8

Character Set

UTF-8

Specification

https://www.hdfgroup.org/

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 10c–5.1) are important:

File

a contiguous string of bytes in a computer store (memory, disk, etc.), and the bytes represent zero or more objects of the model;

Group

a collection of objects (including groups);

Dataset

a multidimensional array of data elements with attributes and other metadata;

Dataspace

a description of the dimensions of a multidimensional array;

Datatype

a description of a specific class of data element including its storage layout as a pattern of bits;

Attribute

a named data value associated with a group, dataset, or named datatype;

Property List

a collection of parameters (some permanent and some transient).

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

11.2.  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 8.

Figure 8 — Outline of the generic data file structure

Figure 8 shows the four levels defined within the HDF encoding as defined in S-100, Part 10c. Below is a further definition of these levels.

Level 1

At the top level lies the Root Group, and it contains the Root Metadata and two subsidiary groups. The Root Metadata applies to all S-100 type products.

Level 2

The next Level contains the Feature Information Group and the Feature Container Group. The Feature Information Group contains the feature BathymetryCoverage and the feature attribute codes. The Feature Container Group contains the Feature Metadata and one or more Feature Instance Groups.

Level 3

This contains a Feature Instance group. A feature instance is a bathymetric gridded data for a single region.

Level 4

This contains the actual data for each feature. In S-102 the BathymetryCoverage uses the ValuesGroup to define the content the other groups at this level are not used.

In Table 7 below, levels refer to HDF5 structuring (see S-100, Part 10c, Figure 10c–9). Naming in each box below the header line is as follows: Generic name; S-100 or S-102 name, or [] if none; and (HDF5 type) group, attribute or attribute list, or dataset.

Table 7 — Overview of S-102 Data Product

Figure 9 — Hierarchy of S-102 Data Product

Table 8 — Root group attributes

The following sections explain entries in Table 7 in greater detail.

12.1.  Introduction

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

Units of Delivery

Exchange Set

Transfer Size

See Section 12.2.2.

Medium Name

Digital Data Delivery

Other Delivery Information

Each dataset must be contained in a physically separate, uniquely identified file on the transfer medium.

Each exchange set has a single exchange catalogue which contains the discovery metadata for each dataset.

An exchange set is encapsulated into a form suitable for transmission by a mapping called an encoding. An encoding translates each of the elements of the exchange set into a logical form suitable for writing to media and for transmission online. An encoding may also define other elements in addition to the exchange set contents (This is media identification, data extents etc. …​) and may define commercial constructs such as encryption and compression methods.

If the data is transformed in S-102 it must not be changed.

This Product Specification defines the encoding which must be used as a default for transmission of data between parties.

The encoding encapsulates exchange set elements as follows:

Mandatory Elements

• S-102 datasets — HDF encoding

• Exchange Catalogue — the XML encoded representation of exchange set catalogue features [discovery metadata].

Optional Elements

• S-102 Feature Catalogue — If it is necessary to deliver the latest Feature Catalogue to the end user it may be done using the S-102 exchange set mechanism for datasets

• S-102 Portrayal Catalogue — If it is necessary to deliver the latest Portrayal Catalogue to the end user it may be done using the S-102 exchange set mechanism for datasets.

12.2.  Dataset

12.3.  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 CATATLOG.XML. No other file in the Exchange Set may be named CATALOG.XML. The contents of the Exchange Catalogue are described in Chapter 13.

12.4.  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.

13.1.  Introduction

The Metadata elements used in the Bathymetric Surface product are derived from S-100 and from ISO 19115:2003 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.

There are only a few elements in the ISO 19115:2003 metadata standard that are mandatory and these relate only to the use of the metadata for identification and pedigree of the data set. A minimum level of data identification is required for all applications including database applications, web services and data set production. However, S-102 requires certain metadata attributes which are used to geolocate the dataset as well as establish a pedigree for the data.

The elements are related in a metadata Schema and include definitions and extension procedures. There exist both mandatory and conditional metadata elements. Only a few metadata elements are mandatory but the inclusion of some of the optional metadata elements establish a situation where other metadata elements are conditionally made mandatory.

Table 14 outlines the core metadata elements (mandatory and recommended optional) required for describing a geographic information data set. The codes indicate: “M” mandatory, “O” optional’ “C” conditional as defined in ISO 19115:2003. Table 14 indicates how the mandatory, optional and conditional core metadata are handled in S-102.

Table 14 — S-102 Handling of Core Metadata Elements

The dataset metadata is stored in a separate file encoded according to the ISO 19115X Schemas. The name of the metadata file is MD_<HDF5 data file base name>.XML (or .xml) ISO metadata (per S-100, Part 10c, Clause 10c–12), The root element in the file is S102_DSMetadataBlock which contains S102_DS_DiscoveryMetadata, S102_StructureMetadataBlock and S102_QualityMetadataBlock.

13.2.  Discovery metadata

Metadata is used for a number of purposes. One high level purpose is for the identification and discovery of data. Every data set needs to be identified so that it can be distinguished from other data sets and so it can be found in a data catalogue, such as a Web Catalogue Service. The discovery metadata applies at the S102_DataSet level. Metadata in S102_DiscoveryMetadataBlock is encoded in a separate metadata file within the S102_DSMetadataBlock.

Figure 10 — S-102 Discovery Metadata

Figure 10 above shows the S102_DiscoveryMetadataBlock. It has a subtype S102_DS_DiscoveryMetadata. This implements the metadata classes from ISO 19115:2003. First implementation classes have been developed corresponding to each of the ISO 19115:2003 classes that have been referenced in which only the applicable attributes have been included. The class S102_DS_DiscoveryMetadata inherits attributes from S-102 specific implementation classes. In addition, an additional component S102_DataIdentification has been added.

This model provides the minimum amount of metadata for a Bathymetry Surface data product. Any of the additional optional metadata elements from the source ISO 19115:2003 metadata standard can also be included.

Table 9 provides a description of each attribute of the S102_DiscoveryMetadataBlock class attributes.

Table 15 — S102_DiscoveryMetadataBlock class attributes

The class S102_DataIdentification provides an extension to the metadata available from ISO 19115:2003. The verticalUncertaintyType attribute was added to accurately describe the source and meaning of the encoded Uncertainty coverage. The depthCorrectionType was also added to define if and how the depths are corrected (that is, true depth, depth ref 1500 m/sec, etc.). Table 16 and Table 17 provide a description.

Table 16 — Code defining the type of sound velocity correction

Table 17 — Code defining how uncertainty was determined

13.3.  Structure metadata

Structure metadata is used to describe the structure of an instance of a collection. Since constraints can be different on separate files (for example they could be derived from different legal sources), or security constraints may be different, the constraint information becomes part of the structure metadata. The other structure metadata is the grid representation and the reference system.

Figure 11 shows the S102_StructureMetadataBlock. The metadata block is generated by the inheritance of attributes from a number of ISO 19115:2003 metadata classes and from two implementation classes for the horizontal and vertical reference system. This makes the metadata block a simple table.

Metadata in S102_StructureMetadataBlock is encoded within a separate metadata xml file under the S102_MetadataBlock root element.

Figure 11 — S-102 Structure Metadata

Table 18 — S102_StructureMetadataBlock class attributes

13.3.1.  Quality metadata

Quality metadata is used to describe the quality of the data in an instance of a collection. Figure 12 shows the S102_QualityMetadataBlock. The S102_QualityMetadataBlock derives directly from the ISO 19115:2003 class DQ_DataQuality. However, its components S102_LI_Source and S102_LI_ProcessStep are generated by the inheritance of attributes from the ISO 19115:2003 classes LI_Scope and LI_ProcessStep. Only some of the attributes of the referenced ISO 19115:2003 classes are implemented.

Metadata in S102_QualityMetadataBlock is encoded within a separate metadata xml file under the S102_MetadataBlock root element.

Figure 12 — S-102 Quality Metadata

Table 19 provides a description of each attribute of the S102_QualityMetadataBlock class attributes and those of its components.

Table 19 — Quality Metadata Block description

Role Name	Name	Description	Mult	Type	Remarks
Class	S102_QualityMetadataBlock	Container class for quality metadata	-	-
attribute	scope	Extent of characteristic(s) of the data for which quality information is reported	1	DQ_Scope
Class	S102_LI_Source	Information about the source data used in creating the data specified by the scope	-	-
attribute	description	Detailed description of the level of the source data	1	CharacterString
attribute	sourceCitation	Recommended reference to be used for the source data	1	CI_Citation	Required items are citation.title and citation.date
Class	S102_LI_ProcessStep	Information about an event or transformation in the life of a dataset including the process used to maintain the dataset	-	-
attribute	dateTime	Date and time or range of date and time on or over which the process step occurred	1	CharacterString
attribute	description	Description of the event, including related parameters or tolerances	1	CharacterString
attribute	processor	Identification of, and means of communication with, person(s) and organization(s) associated with the process step	1	CI_Responsibility	See S-100, Part 4a, Table 4a–2 and S-100, Part 4a, Table 4a–3 for required items
Class	DQ_Scope	Container class for quality metadata	-	-
attribute	level	Hierarchical level of the data specified by the scope	0..*	MD_ScopeCode <<CodeList>>	“dataset” or “tile”
attribute	extent	Information about the horizontal, vertical and temporal extent of the data specified by the scope	0..*	EX_Extent <<DataType>>	Used only if the extent of the data is different from the EX_Extent given for the collection / tile
attribute	levelDescription	Detailed description about the level of the data specified by the scope	1	MD_ScopeDescription <<Union>>

13.4.  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 13, Figure 14, Figure 15 and Figure 16 outline the overall concept of an S-102 Exchange Set for the interchange of geospatial data and its relevant metadata. Figure 13 depicts the realization of the ISO/TS 19139:2007 classes which form the foundation of the Exchange Set. The overall structure of S-102 metadata for Exchange Sets is modelled in Figure 14 and Figure 15. More detailed information about the various classes is shown in Figure 16 and a textual description in Tables 20 to 34.

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 13 — Realization of the Exchange Set classes

Figure 14 — S-102 Exchange Set Catalogue

Figure 15 — S-102 Exchange Set

Figure 16 — 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).

13.5.  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.

13.6.  S102_ExchangeCatalogue

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

The class S102_ExchangeCatalogue is realized from S100_ExchangeCatalogue without modification. S-102 restricts certain attributes and roles as described in Table 20. S102_ExchangeCatalogue is a container substituting for the corresponding S100_ExchangeCatalogue class in the UML diagram. It is needed because S-102 extends S-100 discovery metadata.

Table 20 — S102_ExchangeCatalogue parameters

13.7.  S102_DatasetDiscoveryMetadata

Dataset discovery metadata in S-102 is an extension of the generic S-100 metadata class S100_DatasetDiscoveryMetadata. S-102 adds the attribute griddingMethod which describes the algorithm used to calculate grid values. S-102 also restricts certain attributes and roles as described in Table 23.

Table 23 — S102_DatasetDiscoveryMetadata parameters

13.8.  S102_CatalogueMetadata

The class S102_CatalogueMetadata is realized from S100_CatalogueMetadata without modification. The S-102 class is defined in order to act as a proxy for the corresponding S-100 generic class in S-102 UML diagrams of Exchange Set structure.

Table 32 — S102_CatalogueMetadata parameters