1.3.1  Use of language

Within this document:

1.3.2  Terms and definitions

1.3.3  Abbreviated terms

This Product Specification adopts the following convention for presentation purposes:

1.6.1  Introduction

Changes to S-102 will be released by the IHO as a New Edition, revision, or clarification.

1.6.2  New Edition

New Editions of S-102 introduce significant changes. New Editions enable new concepts, such as the ability to support new functions or applications, or the introduction of new constructs or data types. New Editions are likely to have a significant impact on either existing users or future users of S-102. All cumulative revisions and clarifications must be included with the release of approved New Editions.

1.6.3  Revision

Revisions are defined as substantive semantic changes to S-102. Typically, revisions will change S-102 to correct factual errors; introduce necessary changes that have become evident as a result of practical experience or changing circumstances. A revision must not be classified as a clarification. Revisions could have an impact on either existing users or future users of S-102. All cumulative clarifications must be included with the release of approved revisions.

Changes in a revision are minor and ensure backward compatibility with the previous versions within the same Edition. Newer revisions, for example, introduce new features and attributes. Within the same Edition, a dataset of one version could always be processed with a later version of the Feature and Portrayal Catalogues.

In most cases a new feature or portrayal catalogue will result in a revision of S-102.

1.6.4  Clarification

Clarifications are non-substantive changes to S-102. Typically, clarifications: remove ambiguity; correct grammatical and spelling errors; amend or update cross references; insert improved graphics in spelling, punctuation and grammar. A clarification must not cause any substantive semantic change to S-102.

Changes in a clarification are minor and ensure backward compatibility with the previous versions within the same Edition. Within the same Edition, a dataset of one clarification version could always be processed with a later version of the Feature and Portrayal Catalogues, and a Portrayal Catalogue can always rely on earlier versions of the Feature Catalogue.

1.6.5  Version Numbers

The associated version control numbering to identify changes (n) to S-102 must be as follows:

New Editions denoted as n.0.0

Revisions denoted as n.n.0

Clarifications denoted as n.n.n

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.

4.3.1  Introduction

The S-102 Feature Catalogue describes the feature types, attributes and attribute values which may be used in the product.

The S-102 Feature Catalogue is available in an XML document which conforms to the S-100 XML Feature Catalogue Schema and can be downloaded from the IHO Geospatial Information Registry.

4.3.2  Feature types

S-102 is a coverage feature product. BathymetryCoverage implements S102_DepthCoverage and includes S102_BathymetryValues. QualityOfBathymetryCoverage implements S102_QualityCoverage and includes S102_QualityValues.

4.3.3  Feature relationship

S-102 does not use any feature relationships.

4.3.4  Attributes

4.4.1  Introduction

Bathymetric Surface datasets are represented as regular grids. The general structure for a regular grid is defined in S-100, Part 8. Each sample in a grid represents the value in the grid cell area.

The georeferencing for an S-102 Bathymetric Surface product shall be grid point based, referenced from the southwesternmost grid point. The reference position (grid origin) included in the metadata, precisely the attributes gridOriginLatitude and gridOriginLongitude, 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.

4.4.2  Regular grid

6.1.1  Commission

Commission is applicable for S-102. Data Producers must verify that no excess items have been included in the dataset. Such excess items include duplicate items, which must be removed.

If no excess items are present, the dataset PASSES this test.

6.1.2  Omission

Omission is applicable for S-102. Data Producers must verify that no items that should have been included in the dataset have been omitted.

If no necessary items have been omitted, the dataset PASSES this test.

6.2.1  Conceptual consistency

Conceptual Consistency is applicable for S-102 and follows the guidelines from S-100, Part 1.

Data Producers must verify that the dataset conforms to the S-100 General Feature Model.

If the dataset conforms to the S-100 General Feature Model, the dataset PASSES this test.

6.2.2  Domain consistency

Domain consistency is applicable for S-102 and follows the guidelines from S-100, Part 5.

Data Producers must verify that the dataset conforms to the S-102 Feature Catalogue and to Annex A.

If the dataset conforms to the S-102 Feature Catalogue and to Annex A, the dataset PASSES this test.

6.2.3  Format consistency

Format Consistency is applicable for S-102 and follows the guidelines from S-100, Part 10c.

Data Producers must verify that the dataset conforms to Section 10 of this Product Specification.

If the dataset conforms to Section 10, the dataset PASSES this test.

6.3.1  Gridded data positional accuracy

Gridded positional accuracy is defined by the precision of the positional reference used to specify its location within its spatial projection. These positional references are contained within the spatial metadata of the S-102 grid. It is assumed that any horizontal errors are assimilated into the vertical uncertainty. The vertical values are calculated for each grid point using the processes and procedures used by each hydrographic office during the creation of the S-102 grid. Appropriate selection of both the origin reference point and spatial resolution are important and are another factor in gridded positional accuracy.

6.3.2  Relative internal positional accuracy

The internal positional accuracy is defined as the precision of the location of each grid point within the S-102 grid. The position of each grid point within the grid is referenced by a row and column combination. The metadata for S-102 defines a gridded resolution along both the X and Y axis of the grid. This absolute position of a grid point within the spatial projection of the grid is calculated using the row/column and the X/Y resolution. In this case, the accuracy is controlled by the precision used in defining these resolutions.

6.5.1  Thematic classification correctness

For S-102 bathymetric grids there are two classifications of data values, which are land and water. There are two considerations for assessing classification correctness when using the grid. The first is that values given in the depth layer of the S-102 grid are based on the associated hydrographic office’s chosen vertical datum. Should another value in relation to a different vertical datum be required, a series of correctors would need to be applied. Secondly, when considering the data values, the value stored in the uncertainty for a given grid point must be considered. This uncertainty value represents the magnitude of possible deviation in either direction from the data value and must be applied when assessing the classification correctness. The new value generated when applied may cause a change in the classification.

6.5.2  Non-quantitative attribute accuracy

Thematic accuracy of S-102 bathymetric data is wholly quantitative.

6.5.3  Quantitative attribute accuracy

As defined in S-100, Part 4c the data quality for the depth coverage is also defined as a co-located optional coverage, which is the uncertainty. This value particularly refers to the vertical uncertainty at each grid point. The uncertainty coverage supports multiple definitions of vertical uncertainty.

See Table 10-9.

9.2.1  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 9-2 shows the difference between a sun-illuminated and static (flat) surface.

Informative values for sun azimuth angle and elevation have been provided in Table 9-2 below.

Table 9-2 — Sun Azimuth and Elevation Values

Attribute	Value in Degrees
	Sun-Illuminated	Flat Surface
Sun Azimuth Angle	135 Degrees	0.0 Degrees
Sun Elevation	45 Degrees	0.0 Degrees

10.2.1  Root Group

The root group is required by HDF5. The S-100 HDF5 format (S-100, Part 10c) attaches metadata attributes applicable to the whole dataset to this group. S-102 uses all the S-100 attributes except geographicIdentifier and metaFeatures. The attributes used in S-102 are listed in Table 10-2, with specific requirements, if any, added in the Remarks column.

Table 10-2 — Root group attributes

No	Name	Camel Case	Mult	Data Type	Remarks
1	Product specification number and version	productSpecification	1	String	S-100, Part 10c, Table 6 Example: INT.IHO.S-102.3.0.0
2	Time of data product issue	issueTime	0..1	String (Time format)	S-100, Part 1, Table 2 S-100, Part 10c, Table 1
3	Issue date	issueDate	1	String (Date format)	S-100, Part 1, Table 2 S-100, Part 10c, Table 1
4	Horizontal CRS	horizontalCRS	1	Integer 32-bit	The identifier (EPSG code) of the horizontal CRS as defined in Clause 5.2 (see Clause 10.2.1, Note 2).
5	Epoch of realization	epoch	0..1	String
6a	Bounding box	westBoundLongitude	1	Float 32-bit	The values are in decimal degrees. If a projected CRS is used for the dataset, these values refer to those of the baseCRS underlying the projected CRS (see Clause 10.2.1, Note 3). The root bounding box needs to encompass all data, including fill values. The outermost cell boundaries of the grid cells and the bounding box / domain extent polygon of each feature instance group form the basis for the root bounding box.
6b		eastBoundLongitude	1	Float 32-bit
6c		southBoundLatitude	1	Float 32-bit
6d		northBoundLatitude	1	Float 32-bit
7	Metadata	metadata	0..1	String	Name of metadata file MD_<HDF5/>file base name>.XML (or .xml) ISO metadata (per S-100, Part 10c, Clause 12 & S-100, Part 8).
8	Vertical coordinate system	verticalCS	1	Integer 32-bit	Mandatory in S-102. EPSG code; The only allowed value is: *6498 (Depth—​metres—​orientation down)
9	Vertical coordinate base	verticalCoordinateBase	1	Enumeration	Mandatory in S-102. The only allowed value is 2: verticalDatum (see S-100, Part 10c, Table 22).
10	Vertical datum reference	verticalDatumReference	1	Enumeration	Mandatory in S-102. The only allowed value is 1: s100VerticalDatum (see S-100, Part 10c, Table 23).
11	Vertical datum	verticalDatum	1	Integer unsigned 16-bit	Numeric code from IHO GI Registry Vertical Datum attribute $1-30$ & 44 see Clause 10.2.1, Note 4
NOTE 1  The productIdentifier (“S-102”) and version fields (X.X.X) of S100_ProductSpecification must be used. NOTE 2  The value horizontalCRS specifies the horizontal Coordinate Reference System. At the time of writing, S-100 does not yet provide a mechanism for this value’s definition within HDF5 encoding (such as an enumeration of horizontal CRSs). Consequently, this configuration causes a deviation from S-100. The horizontal datum is implicitly defined by this CRS because each horizontal CRS consists of a coordinate system and a datum. S-102 does not use “user defined” CRS as mentioned in S-100, Part 10c, Table 6. NOTE 3  The baseCRS is the geodetic CRS on which the projected CRS is based. In particular, the datum of the base CRS is also used for the derived CRS (see S-100, Part 6, Table 6). NOTE 4  This is the default vertical datum. If and only if a BathymetryCoverage feature instance group does not specify a vertical datum, this (Root Group) vertical datum shall apply.

10.2.2  Feature Codes (Group_F)

No attributes.

This group specifies the S-100 features to which the data applies, and consists of three components:

featureCode — a 1-dimensional dataset with the featureCode(s) of the S-100 feature(s) contained in the data product. For S-102, the dataset has only two elements — the string “BathymetryCoverage” and “QualityOfBathymetryCoverage” (without quotes). The entries in this dataset give the names of the other two components of Group_F.

BathymetryCoverage — A 1-dimensional dataset that contains the standard definition of the bathymetry coverage feature class in terms of its attributes and their types, units of measure, etc. The datatype of its elements is the compound type described in S-100, Part 10c, Table 8.

QualityOfBathymetryCoverage — A 1-dimensional dataset of the same datatype as the BathymetryCoverage dataset described above. This QualityOfBathymetryCoverage dataset contains the definition of the reference to metadata records. The reference is a single integer which identifies a metadata record in featureAttributeTable (described in S-100, Part 10c, Clause 9.6.2 and Clause 10.2.8.

10.2.3  BathymetryCoverage and QualityOfBathymetryCoverage Tables (in Group_F)

BathymetryCoverage and QualityOfBathymetryCoverage are arrays of compound type elements, whose components are the 8 components specified in Table 10-3.

Table 10-3 — Sample contents of the BathymetryCoverage and QualityOfBathymetryCoverage arrays

Name	Explanation	BathymetryCoverage		QualityOfBathymetryCoverage
		S-100 Attribute 1	S-100 Attribute 2	S-100 Attribute 1
code	Camel Case code of attribute as in Feature Catalogue	depth	uncertainty	iD
name	Long name as in Feature Catalogue	depth	uncertainty	ID
uom.name	Units (uom.name from S-100 Feature Catalogue)	metres	metres	(empty)
fillValue	Fill value (integer or float, string representation, for missing values)	1000000	1000000	0
datatype	HDF5 datatype, as returned by H5Tget_class() function	H5T_FLOAT	H5T_FLOAT	H5T_INTEGER
lower	Lower bound on value of attribute	-14	0	1
upper	Upper bound on value of attribute	11050	(empty)	(empty)
closure	Open or Closed data interval. See S100_IntervalType in S-100, Part 1.	closedInterval	geSemiInterval	geSemiInterval
NOTE  The uncertainty attribute of BathymetryCoverage may be omitted under certain conditions. See Clause 10.2.7.

According to S-100, Part 10c, Clause 9.5, “All the numeric values in the feature description dataset are string representations of numeric values; for example, “-9999.0” not the float value -9999.0.”

While the sample contents are shown in the two attributes columns, these are actually rows in the BathymetryCoverage table. They are also each a single HDF5 compound type and represent a single HDF5 element in the table.

All cells shall be HDF5 variable length strings. The minimum and maximum values are stored in lower and upper columns. Variable length strings allow future proofing the format in the event editing is allowed or correcting these values is required.

10.2.4  Root BathymetryCoverage

Table 10-4 — Attributes of BathymetryCoverage feature container group

No	Name	Camel Case	Mult	Data Type	Remarks
1	Data organization index	dataCodingFormat	1	Enumeration	Value: 2
2	Dimension	dimension	1	Integer unsigned 8-bit	Value: 2
3	Common point rule	commonPointRule	1	Enumeration	Value: 2 (low) see S-100, Part 8, Table 11.
4	Horizontal position uncertainty	horizontalPositionUncertainty	1	Float 32-bit	Value: -1.0 (if unknown or not available)
5	Vertical position uncertainty	verticalUncertainty	1	Float 32-bit	Value: -1.0 (if unknown or not available)
6	Number of feature instances	numInstances	1	Integer unsigned 8-bit	This is the total number of Feature Instance Groups within the Feature Container Group. The minimum is 1. see Clause 10.2.4, Note
7a	Sequencing rule	sequencingRule.type	1	Enumeration	Value: 1 (linear) see S-100, Part 8, Table 12.
7b		sequencingRule.scanDirection	1	String	Value: <axisNames entry> (comma-separated). For example, “latitude,longitude”. Reverse scan direction along an axis is indicated by prefixing a ‘-’ sign to the axis name. See Clause 4.2.1.1.8.3
8	Interpolation type	interpolationType	1	Enumeration	Value: 1 (nearestneighbor). See S-100, Part 8, Table 13
9	Offset of data point in cell	dataOffsetCode	1	Enumeration	Value: 5 barycenter (centroid) of cell. See S-100, Part 10c, Table 10
NOTE  The number depends on the number of different vertical datums in the Feature Container Group.

10.2.5  Feature Instance group — BathymetryCoverage.nn

The BathymetryCoverage Feature Container Group can contain one or more Feature Instance Groups. The naming of the Feature Instance Groups follows the notation specified by the S-100. For generalization, the numbering is indicated with “.nn”.

Each feature instance group implements a unique vertical datum. All feature instance groups must share the same spatial location and extent. For each feature instance group, only the grid cells falling within the area of validity for that feature instance group’s vertical datum should be populated with (real) data. Within that feature instance group, all other grid cells should be populated with the fill value. Therefore, it is expected that:

As derived from S-100, Part 10c, Clause 9.7 and S-100, Part 10c, Table 12, Table 10-5 and Table 10-6 describe the structure and attributes, respectively, of the BathymetryCoverage feature instance group.

Table 10-5 — Structure of BathymetryCoverage feature instance group

Group	HDF5 Category	Name	Mult	Data Type	Remarks / Data Space
/BathymetryCoverage/ BathymetryCoverage.01	attributes	(see Remarks)	1	(see Remarks)	Single-valued attributes as descripted in Table 10-6
	Dataset	domainExtent.polygon	0..1	Compound (Float, Float)	Spatial extent of the domain of the coverage Array (1-d): i=0, P Components: <longitude/>, latitude> or <X/>, Y> (coordinates of bounding polygon vertices as a closed ring; that is, the first and last elements will contain the same values) Either this or the bounding box attribute must be populated.
/BathymetryCoverage/ BathymetryCoverage.nn	attributes	(see Remarks)	1	(see Remarks)	Single-valued attributes as descripted in Table 10-6
	Dataset	domainExtent.polygon	0..1	Compound (Float, Float)	Spatial extent of the domain of the coverage Array (1-d): i=0, P Components: <longitude/>, latitude> or <X/>, Y> (coordinates of bounding polygon vertices as a closed ring; that is, the first and last elements will contain the same values) Either this or the bounding box attribute must be populated.

Table 10-6 — Attributes of BathymetryCoverage feature instance group

No	Name	Camel Case	Mult	Data Type	Remarks
1a	Bounding box	westBoundLongitude	0..1	Float 32-bit	Coordinates should refer to the previously defined Coordinate Reference System. Either this or the domainExtent.polygon dataset must be populated
1b		eastBoundLongitude	0..1	Float 32-bit
1c		southBoundLatitude	0..1	Float 32-bit
1d		northBoundLatitude	0..1	Float 32-bit
2	Number of groups	numGRP	1	Integer unsigned 8-bit	The number of data values groups contained in this instance group. Value: 1
3	Longitude of grid origin	gridOriginLongitude	1	Float 64-bit	Longitude or easting of grid origin. Unit: (to correspond with previously defined Coordinate Reference System)
4	Latitude of grid origin	gridOriginLatitude	1	Float 64-bit	Latitude or northing of grid origin. Unit: (to correspond with previously defined Coordinate Reference System)
5	Grid spacing, longitude	gridSpacingLongitudinal	1	Float 64-bit	Cell size in x dimension.
6	Grid spacing, latitude	gridSpacingLatitudinal	1	Float 64-bit	Cell size in y dimension.
7	Number of points, longitude	numPointsLongitudinal	1	Integer unsigned 32-bit	Number of points in x dimension.
8	Number of points, latitude	numPointsLatitudinal	1	Integer unsigned 32-bit	Number of points in y dimension.
9	Start sequence	startSequence	1	String	Grid coordinates of the grid point to which the first in the sequence of values is to be assigned. The choice of a valid point for the start sequence is determined by the sequencing rule. Format: n, n Example: “0,0” (without quotes)
10	Vertical datum	verticalDatum	0..1	Integer unsigned 16-bit	see remark Table 10-2 row vertical datum and [mvdvdr] Mandatory for feature instance groups with a different vertical datum from that specified in the Root Group (prohibited otherwise)
11	Vertical datum reference	verticalDatumReference	0..1	Integer unsigned 8-bit	The only allowed value is 1: s100VerticalDatum (see S-100, Part 10c, Table 23). see [mvdvdr] Mandatory if this value were to differ from what is contained in the Root Group

The gridOriginLongitude, gridOriginLatitude, gridSpacingLongitudinal, and gridSpacingLatitudinal attributes should be in the same geographic units as the bounding box. Note that this practice deviates from S-100 where it indicates that this value should be in Arc Degrees.

numPointsLongitude and numPointsLatitude must contain the number of cells in the x and y dimensions of the values table.

The S-102 uses the “Overriding of Attributes” concept of the S-100, Part 10c, Clause 9.7.1. This usage allows the feature instance group to overwrite the attributes of a higher group, in this case the verticalDatum. The default vertical datum is specified in the root group (see Table 10-2). The feature instance group for this default vertical datum must not use the additional attributes verticalDatum and verticalDatumReference (on the feature instance group).

If multiple vertical datums are present in the product, a separate feature instance group must be created for each vertical datum. These feature instance groups must use the additional attribute verticalDatum (on the feature instance group).

Note: At present, this Product Specification does not allow values other than 1: s100VerticalDatum for verticalDatumReference. However, if future changes allow the value of 2: EPSG (and if the value at the feature instance group differs from what is contained in the Root Group), then this value would become mandatory.

According to S-100, either the BoundingBox at the Feature Instance Group or the domainExtent.polygon must be specified. If domainExtent.polygon is specified, the BoundingBox is not specified in this case. The grid cells that do not belong to the area of the respective vertical datum should be assigned the fill value. If more than one domainExtent.polygon is used, those of different feature instance groups should not overlap. At positions where the polygons of different Feature Instance groups touch, the edges should be identical. The domainExtent.polygon does not have to follow grid cell boundaries but is an independent vector geometry based on the SoundingDatum surface from S-101. The domainExtent.polygon only supports a simple polygon geometry in accordance with S-100, Part 10c, Table 11. The mapping of multi-polygons and inner rings is not possible.

10.2.6  The values group — Group_001

This group contains 5 attributes, all of which are mandatory. According to S-100, Part 10c, Table 19, timePoint applies because the dataCodingFormat = 2. The other four attributes for this group are an extension of this Product Specification and, thus, are not defined by S-100, Part 10c. Table 10-7 lists all 5 attributes.

Table 10-7 — Attributes of values group

No	Name	Camel Case	Mult	Data Type	Remarks
1	minimum Depth	minimumDepth	1	Float 32-bit	The minimum depth value in the values dataset(s) of this group
2	maximum Depth	maximumDepth	1	Float 32-bit	The maximum depth value in the values dataset(s) of this group
3	minimum Uncertainty	minimumUncertainty	1	Float 32-bit	The minimum uncertainty value in the values dataset(s) of this group. If no uncertainty values are in the dataset(s) the value must be the fillValue
4	maximum Uncertainty	maximumUncertainty	1	Float 32-bit	The maximum uncertainty value in the values dataset(s) of this group. If no uncertainty values are in the dataset(s) the value must be the fillValue
5	Time stamp	timePoint	1	String	Because S-102 specifies survey dates elsewhere in its structure, this value should always be the fill value: 00010101T000000Z

The group contains an HDF5 dataset named values containing the bathymetric gridded data.

10.2.7  BathymetryCoverage feature instance group — values dataset

This dataset contains the compound data arrays containing bathymetric gridded data. These components are explained below.

For bathymetric gridded data, the dataset includes a two-dimensional array containing always the depth and under certain conditions uncertainty data. These dimensions are defined by numPointsLongitudinal and numPointsLatitudinal. By knowing the grid origin and the grid spacing, the position of every grid point and grid cell can be simply computed.

If the uncertainty for each grid cell is equal, it is not necessary to store it at each cell in the grid. The uniqueness of the uncertainty results from the equality of the attributes minimumUncertainty and maximumUncertainty of Group_001 of the BathymetryCoverage (see Table 10-7 No. 3 & 4). If the uncertainty values at the grid cells are omitted, it must be ensured that the entry of the uncertainty of the BathymetryCoverage in the Group_F is also omitted (see Table 10-3). This type of storage technique can reduce the amount of memory required for the uncertainty without loss of information. The uncertainty of each grid cell can be immediately obtained from the minimumUncertainty or maximumUncertainty attributes of Group_001 of the BathymetryCoverage.

If the uncertainty is not the same for each grid cell, it must be stored at each cell in the grid. For unknown or unused uncertainty data, it must be filled with the fillValue specified in the Group_F feature information dataset.

The grid cell values are stored in two-dimensional arrays with a prescribed number of columns (numCOL) and rows (numROW). This grid is defined as a regular grid (dataCodingFormat = 2); therefore, the depth and uncertainty values will be for each cell in the grid. The data type of the array values is a compound with one or two members.

10.2.8  Root QualityOfBathymetryCoverage

The QualityOfBathymetryCoverage container group has the same metadata attributes as BathymetryCoverage container group (see Table 10-4). The values of the attributes must also be the same as the BathymetryCoverage container group. An exception is the attribute dataCodingFormat, which must be ‘9’. The use of multiple BathymetryCoverage Feature Instance groups (different Vertical Datums) does not affect the multiplicity of the QualityOfBathymetryCoverage, which remains 0 to 1. This means that the different BathymetryCoverage Feature Instance groups share a common QualityOfBathymetryCoverage.

The QualityOfBathymetryCoverage container group contains an additional 1-dimensional array named featureAttributeTable (S-100, Part 10c, Table 9; S-100, Part 10c, Clause 9.6.2). This dataset is mandatory within the QualityOfBathymetryCoverage group. Each element of this array is a metadata record of HDF5 compound type. The fields are described in Table 10-8 below.

Table 10-8 — Elements of featureAttributeTable compound datatype

No	Attribute	Description	Mult	Data Type	Remarks
1	id	Metadata record identifier	1	Integer unsigned 32-bit	Each record must have a unique identifier.
2	dataAssessment	The categorization of the assessment level of bathymetric data for an area.	0..1	Integer unsigned 8-bit	*1: Assessed *2: Unassessed *3: Oceanic
3	featuresDetected.leastDepthOfDetectedFeaturesMeasured	Expression stating if the least depth of detected features in an area was measured.	0..1	Integer unsigned 8-bit	Boolean, Values: *1 (TRUE) *0 (FALSE). See Clause 10.2.8, Note 1.
4	featuresDetected.significantFeaturesDetected	A statement expressing if significant features have or have not been detected in the course of a survey.	0..1	Integer unsigned 8-bit	Boolean, Values: *1 (TRUE) *0 (FALSE). See Clause 10.2.8, Note 2.
5	featuresDetected.sizeOfFeaturesDetected	The size of detected bathymetric features in an area.	0..1	Float 32-bit	See Clause 10.2.8, Note 3 and Clause 10.2.8, Note 4.
6	featureSizeVar	Percentage of depth that a feature of such size could be detected.	0..1	Float 32-bit	Set to zero if the feature size does not scale with depth. See Clause 10.2.8, Note 3 and Clause 10.2.8, Note 4.
7	fullSeafloorCoverageAchieved	Expression stating if full seafloor coverage has been achieved in the area by hydrographic surveys.	0..1	Integer unsigned 8-bit	Boolean, Values: *1 (TRUE) *0 (FALSE). See Clause 10.2.8, Note 5.
8	bathyCoverage	False for grid cells populated by interpolation.	0..1	Integer unsigned 8-bit	Boolean, Values: *1 (TRUE) *0 (FALSE). See Clause 10.2.8, Note 6.
9	zoneOfConfidence.horizontalPositionUncertainty.uncertaintyFixed	The best estimate of the fixed horizontal or vertical accuracy component for positions, depths, heights, vertical distances, and vertical clearances.	0..1	Float 32-bit
10	zoneOfConfidence.horizontalPositionUncertainty.uncertaintyVariableFactor	The factor to be applied to the variable component of an uncertainty equation so as to provide the best estimate of the variable horizontal or vertical accuracy component for positions, depths, heights, vertical distances, and vertical clearances.	0..1	Float 32-bit
11	surveyDateRange.dateStart	The start date of the period of the hydrographic survey.	0..1	Date	ISO 8602:2004 date format. Complete or truncated date, see S-100, Part 1, Table 2.
12	surveyDateRange.dateEnd	The end date of the period of the hydrographic survey.	0..1	Date	ISO 8602:2004 date format. Complete or truncated date, see S-100, Part 1, Table 2.
13	sourceSurveyID	The survey filename or ID.	0..1	String
14	surveyAuthority	The authority which was responsible for the survey.	0..1	String
15	typeOfBathymetricEstimationUncertainty	The measure used to estimate the magnitude of the difference between true and estimated bathymetric depth, after all appropriate corrections are made.	0..1	Enumeration	See Table 10-9. See Clause 10.2.8, Note 7.
NOTE 1  A feature in this context is any object, whether manmade or not, projecting above the sea floor, which may be a danger for surface navigation S-44. Least depth of detected features measured does not describe the least depth of features that were actually detected during a hydrographic survey, but the ability of the survey to detect the least depth of features with a maximum uncertainty as defined in S-44. NOTE 2  A feature in this context is any object, whether manmade or not, projecting above the sea floor, which may be a danger for surface navigation S-44. Significant features detected does not describe if significant features were actually detected during a hydrographic survey, but whether the survey had the capacity to detect significant features. NOTE 3  The role of the attribute, featureSizeVar is described in Clause 7.1. The expectation is that featureSizeVar will be set to zero if the feature size does not scale with depth. As with featureSize, featureSizeVar should be ignored if significantFeatures is False. NOTE 4  When both featureSize and featureSizeVar are present, the greater of the two should be considered valid. NOTE 5  Full seafloor coverage achieved applies to both the spatial completeness of feature detection and to the spatial completeness of the measurement of the regular seafloor. The former is further specified by the complex attribute features detected; the latter by the attributes depth range maximum value and depth range minimum value. NOTE 6  The attribute bathyCoverage is especially useful in side-scan surveys which are characterized by gaps in bathymetric observations with full coverage side-scan imagery. In this case, interpolated gaps between bathymetry coverage would show fullSeafloorCoverageAchieved = True and bathyCoverage = False. However, if fullSeafloorCoverageAchieved = False, bathyCoverage must also equal False (e.g., gaps between single beam echosounder data without correlating side-scan sonar coverage). NOTE 7  Names and listed values which are not currently defined in the IHO GI Registry are subject to change upon acceptance in the Registry.

Table 10-9 — Codes defining how uncertainty of bathymetric depth was determined

Role Name	Name	Description	Code	Remarks
Enumeration	S102_BatymetricUncertaintyType	An estimate of the magnitude of the difference between true and estimated bathymetric depth, after all appropriate corrections are made.	-
Value	rawStandardDeviation	Raw standard deviations of soundings that contributed to the grid cell.	1	-
Value	cUBEStandardDeviation	Standard deviation of soundings captured by a CUBE hypothesis (that is, CUBE’s standard output of uncertainty).	2	-
Value	productUncertainty	The greater of (1) standard deviation of the soundings contributing to the depth solution or, (2) the a priori computed uncertainty estimate (that is, modelled Total Vertical Uncertainty).	3	-
Value	historicalStandardDeviation	Estimated standard deviation based on historical/archive data.	4	-
Value	(fill value representing “unknown”)	(fill value when the uncertainty is an unknown layer type)	0	This is a “fill value” and will not be in the feature catalogue.

10.2.9  Instance group QualityOfBathymetryCoverage.01

The QualityOfBathymetryCoverage.01 instance group has the same metadata attributes as BathymetryCoverage.01 instance group (see Table 10-6). The values of the attributes must also be the same as the BathymetryCoverage instance group.

10.2.10  Values group for QualityOfBathymetryCoverage

The values group for QualityOfBathymetryCoverage contains no metadata attributes and a single dataset named values, which is described in Clause 10.2.11.

10.2.11  Values dataset for QualityOfBathymetryCoverage

The values dataset for QualityOfBathymetryCoverage is a single two-dimensional array of unsigned integers (the same datatype and size as the “id” field in featureAttributeTable — Table 10-7). The array must have the same dimensions as the values dataset in the BathymetryCoverage feature instance (Clause 10.2.7).

Each cell in this values dataset must be populated with a value that is one of the record identifiers in the featureAttributeTable dataset or with the fill value 0 (zero).

10.2.12  Mandatory Naming Conventions

The following group and attribute names are mandatory in S-100:

11.2.1  Dataset management

Three types of dataset files may be produced and contained within an exchange set:

11.2.2  Dataset size

S-102 delivery will take place in one form: network transfer to platform (that is, internet download). An example scenario has been provided below:

Table 11-1 provides general information to aid in the compilation of S-102 data for specific charting scales.

11.2.3  Dataset file naming

Dataset naming must follow a standard pattern to give implementers greater predictability of incoming datasets (see S-100, Part 17, Clause 4.3). S-102 dataset naming conventions must follow these rules.

11.5.1  Use of compression

The data producer decides if compression will be used on the S-102 product files (HDF5). It is expected that a hydrographic office will make a policy decision and that all the S-102 datasets from the producer will be either compressed or uncompressed.

It is recommended to compress all the dataset files, for example HDF5 files. The ZIP compression method defined in S-100, Part 15, Clause 5.2 must be applied to the product files.

11.5.2  Use of data protection

It is recommended to encrypt all the dataset files, for example HDF5. The encryption method defined in S-100, Part 15 must be applied.

11.5.3  Use of digital signatures

Digital signatures shall be used on all files included in a S-102 compliant Exchange Set to meet the requirements of IMO resolution MSC.428(98) to reduce cyber security risks among users, especially when used in navigations systems at sea. The recommended signature method is defined in S-100, Part 15.

The digital signature information is encoded in the corresponding discovery block in the exchange catalogue for each file included in the Exchange Set.

12.4.1  S100_ExchangeCatalogueIdentifier

S-102 uses S100_ExchangeCatalogueIdentifier without modification.

12.4.2  S100_CataloguePointOfContact

S-102 uses S100_CataloguePointOfContact without modification.

12.5.1  S100_NavigationPurpose

S-102 uses S100_NavigationPurpose without modification.

12.5.2  S100_DataCoverage

S-102 uses S100_DataCoverage without modification, but with additional remarks and changes to the multiplicity.

Table 12-2 — S100_DataCoverage parameters

Role name	Name	Description	Mult	Type	Remarks
Class	S100_DataCoverage	A spatial extent where data is provided along with the display scale information for the provided data	-	-	This field is used by user systems as part of the data loading and unloading algorithms, and it is strongly encouraged that Product Specifications mandate the use of one or more of the displayScale provided as part of S100_DataCoverage.
Attribute	boundingPolygon	A polygon which defines the actual data limit	1	EX_BoundingPolygon	Clause 12.5.2, Note
Attribute	temporalExtent	Specification of the temporal extent of the coverage	0	S100_TemporalExtent	The temporalExtent is not used in S-102.
Attribute	optimumDisplayScale	The scale at which the data is optimally displayed	0..1	Integer	Example: A scale of 1:25000 is encoded as 25000
Attribute	maximumDisplayScale	The maximum scale at which the data is displayed	0..1	Integer
Attribute	minimumDisplayScale	The minimum scale at which the data is displayed	0..1	Integer
Attribute	approximateGridResolution	The resolution of gridded or georeferenced data (in metres)	1..2	Real	Mandatory in S-102 A single value may be provided when all axes have a common resolution. For multiple value provision, use axis order as specified in dataset. For example, for 5 metre resolution, the value 5 must be encoded. If the grid cell size varies over the extent of the grid (i.e., when using a geographic grid), an approximated value should be used.
NOTE  boundingPolygon is restricted to a single GML Polygon with one exterior and 0 or more interiors expressed as Linear Rings using SRS EPSG:4326. The exterior and optional interiors shall be composed of a closed sequence of >=4 coordinate positions expressed individually or as a list (posList). The GML polygon shall have a valid GML identifier.

12.5.3  S100_Purpose

S-102 uses S100_Purpose without modification, but with a restriction on the allowed values.

Table 12-3 — S100_Purpose

Role name	Name	Description	Code	Remarks
Enumeration	S100_Purpose	The purpose of the dataset	-	The S-100 values update, reissue, and delta are not used in S-102.
Value	newDataset	Brand new dataset	1	No data has previously been produced for this area.
Value	newEdition	New edition of the dataset or Catalogue	2	Includes new information which has not been previously distributed by updates.
Value	cancellation	Dataset or Catalogue that has been cancelled	5	Indicates the dataset or Catalogue should no longer be used and can be deleted.

12.5.4  S100_EncodingFormat

S-102 uses S100_EncodingFormat with a restriction on the allowed values to permit only the S-100 HDF5 format for S-102 datasets.

Table 12-4 — S100_EncodingFormat parameters

Role name	Name	Description	Code	Remarks
Enumeration	S100_EncodingFormat	The encoding format	-	The only value allowed in S-102 is “HDF5”.
Value	HDF5	The HDF5 data format as defined in S-100, Part 10c	3	-

12.5.5  S100_ProductSpecification

S-102 uses S100_ProductSpecification without modification, but with additional remarks and changes to the multiplicity.

Table 12-5 — S100_ProductSpecification parameters

Role name	Name	Description	Mult	Type	Remarks
Class	S100_ProductSpecification	The Product Specification contains the information needed to build the specified product.	-	-	-
Attribute	name	The name of the Product Specification used to create the datasets	1	CharacterString	The name in the GI Registry should be used for this field. For S-102, this name is “Bathymetric Surface” (as of 25 June 2024).
Attribute	version	The version number of the Product Specification	1	CharacterString	TR 2/2007 specifies versioning of Product Specifications Example: 3.0.0 for S-102 Edition 3.0.0
Attribute	date	The version date of the Product Specification	1	Date	-
Attribute	productIdentifier	Machine readable unique identifier of a product type	1	CharacterString (Restricted to Product ID values from the IHO Product Specification Register in the IHO Geospatial Information (GI) Registry)	For S-102, this identifier is “S-102” (without quotes).
Attribute	number	The number used to lookup the product in the Product Specification Register of the IHO GI registry	1	Integer	For IHO Product Specifications, these numbers should be taken from the IHO Product Specification Register in the IHO GI Registry. The corresponding Idx-number of the IHO Registry for S-102 Ed. 3.0.0 is 215.
Attribute	compliancyCategory	The level of compliance of the Product Specification to S-100	0..1	S100_CompliancyCategory	See S-100, Part 4a, Clause 4a–5.5 and Clause 12.5.6 below.

12.5.6  S100_CompliancyCategory

S-102 exchange sets conforming to this edition of S-102 and using a CRS from the EPSG registry may be encoded as category 3 or 4 when the compliancyCategory metadata attribute is populated. Because S-98 interoperability assumes category4 datasets, category4 may be used for test purposes, though the absence of test datasets and of a published IHO interoperability catalogue mean this edition of S-102 does not yet qualify for category4. Given the uncertainty about interoperability testing requirements and availability of test datasets, the S-100 WG chair and S-102 PT chair should be consulted for up-to-date guidance.

Table 12-6 — S100_CompliancyCategory

Role Name	Name	Description	Code	Remarks
Enumeration	S100_CompliancyCategory	-	-	S-102 should use category3 or category4, subject to the guidance provided in Clause 12.5.6.
Value	category3	IHO S-100 compliant with standard encoding	3	Qualifies as category2; plus “The Product Specification uses only an encoding method defined in S-100, Part 10 and Part 4a, Clause 5.5.3”
Value	category4	IHO S-100 and IMO harmonized display compliant	4	Qualifies as category3; plus additional requirements, including a portrayal catalogue, cybersecurity (digital signatures and encryption), test material, use of a CRS from the EPSG Registry, and compliance with the IHO S-98 interoperability catalogue. S-100, Part 4a, Clause 5.5.4

12.5.7  S100_ProtectionScheme

S-102 uses S100_ProtectionScheme without modification.

12.8.1  S100_CatalogueScope

S-102 uses S100_CatalogueScope without modification.

12.8.2  PT_Locale

S-102 uses PT_Locale without modification. The class PT_Locale is defined in ISO 19115-1:2014/Amd 1:2018. LanguageCode, CountryCode, and MD_CharacterSetCode are ISO codelists which are defined in a codelists file which is part of the S-100 Edition 5.2.0 schema distribution.