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OGC Abstract Specification Topic

Topic 21 - Discrete Global Grid Systems - Part 1 Core Reference system and Operations and Equal Area Earth Reference System
Robert Gibb Editor
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OGC Abstract Specification Topic

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Document number:20-040r3
Document type:OGC Abstract Specification Topic
Document subtype:Conceptual Model
Document stage:Approved
Document language:English

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I.  Abstract

This Abstract Specification lays the foundations for Discrete Global Grid Systems (DGGS). It defines Common classes for spatio-temporal geometry, topology, and reference systems using identifiers, a DGGS Core Reference system as a reference system using zonal identifiers with structured geometry that may be spatio-temporal, a suite of DGGS Core Functions, and it specifies Equal-Area Earth DGGS. The OGC DGGS Abstract Specification supports the specification of standardized DGGS infrastructures that enable the integrated analysis of very large, multi-source, multi-resolution, multi-dimensional, distributed geospatial data. Interoperability between OGC DGGS implementations is anticipated through implementation standards, and extension interface encodings of OGC Web Services.

II.  Keywords

The following are keywords to be used by search engines and document catalogues.

ogcdoc, OGC document, Discrete Global Grid System, DGGS, Digital Earth, DGGS-core, Spatial Reference System, Global Data Structure, Geographic Information Systems, DE-9IM, standard, specification


III.  Preface

This document is consistent with the first edition ISO 19170-1:2020, Geographic Information — Discrete Global Grid Systems Specifications — Core Reference System and Operations, and Equal Area Earth Reference System. ISO/DIS 19170-1:2020 was prepared by Technical Committee ISO/TC 211, Geographic information/Geomatics, in close collaboration with the Open Geospatial Consortium (OGC). It replaces the first OGC edition published as document 15-104r5.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. The Open Geospatial Consortium shall not be held responsible for identifying any or all such patent rights.

Recipients of this document are requested to submit, with their comments, notification of any relevant patent claims or other intellectual property rights of which they may be aware that might be infringed by any implementation of the standard set forth in this document, and to provide supporting documentation.

IV.  Security considerations

No security considerations have been made for this document.

V.  Submitting Organizations

The following organizations submitted this Document to the Open Geospatial Consortium (OGC):

VI.  Submitters

All questions regarding this submission should be directed to the editor or the submitters:

.

Name Representing OGC member
Joseph Bell Geoscience Australia Yes
Chenqi Cheng Peking University Collaborative Innovation Center for Geospatial Big Data Yes
Robert Gibb (ed.) Manaaki Whenua — Landcare Research, New Zealand Yes
Perry Peterson University of Calgary Yes
Matthew Purss Pangaea Innovations Pty Ltd Yes
Fuhu Ren Peking University Collaborative Innovation Center for Geospatial Big Data Yes
Faramarz Samavati University of Calgary Yes
Peter Strobl Joint Research Centre (JRC) Yes

VII.  Foreword

This second OGC edition of Abstract Specification Topic 21 — Discrete Global Grid Systems replaces the first edition (OGC 15-104r5), which has been technically revised.

The changes in this edition compared to the previous OGC edition are:

Further details are given in Annex D and Annex E.

VIII.  Introduction

DGGSs (Discrete Global Grid Systems) provide a new way to organise, store and analyse spatio-temporal data. This document contains a normative definition for DGGS and informative annexes. Annex B discusses the theoretical basis for equal area Earth DGGS, and Annex C discusses DGGS’s historical background. At the heart of DGGS is a new Referencing system. Spatial and temporal RSs described elsewhere by ISO/TC211 and the OGC (Open Geospatial Consortium) fall into two types:

  1. Referencing by coordinates (ISO 19111:2019), and

  2. Referencing by identifiers (geographic in ISO 19112:2019 & ordinal era in ISO 19108:2002).

In spatial Referencing by identifiers, the only required geometry is an extent, which may be expressed as a simple bounding box. Formal geometry need not be defined and sometimes follows societal whim. Similarly in ordinal temporal RSs, the topology of ordinal era’s are known, but the start and finish times are often only an estimation and are not required by the data model. DGGSs introduce a third type — Referencing by identifiers with structured geometry, illustrated in Figure 1. A single parent global geometry is chosen to define the dimensionality and orientation of the region of space-time occupied by the DGGS — it’s global world.

Figure 1 — Referencing by identifiers with structured geometry

The structure for the DGGS geometry is provided by a strictly controlled process of recursive tessellation of the parent geometry that creates the DGGS RS’s units of geometry. The region occupied by each unit of geometry is called a zone. Each zone is given a unique name, called a zonal identifier. Each zonal identifier is associated with a representative spatio-temporal position in a base CRS (coordinate reference system) defined by a datum for the DGGS’s global world. Best practice is for a zonal identifier to be an encoding of both its position and its topology. Referencing by identifiers with structured geometry gives rise to RSs using zonal identifiers with structured geometry. Geographic information is inherently four-dimensional and includes time. So, a unified spatio-temporal data model for coordinate systems, geometry, topology, identifiers and RSs using identifiers is a pre-requisite for spatio-temporal DGGSs.

The approach taken in this document to specifying spatio-temporal data classes is to apply the spatio-temporal data model pattern in ISO 19111:2019 to spatial data classes in both ISO 19107:2019 and ISO 19112:2019 to produce their spatio-temporal equivalents. The set of common spatio-temporal classes for geometry, topology, identifiers, and RSs using identifiers specified in this document are therefore consistent with spatio-temporal CRS and coordinate systems in ISO 19111. Like ISO 19111, the temporal data model in this document does not reference ISO 19108:2002. The similarities and differences are described in Annex D.

In this document the spatio-temporal scope is constrained to spatial classes that are invariant through all time, and to temporal classes that are invariant throughout space. While this approach excludes certain spatio-temporal situations, it is flexible enough for a very large body of social and environmental modelling. Oceanic, climate and weather modelling often need geometries with a constant mass of gaseous fluid under changing pressure and temperature. These models can be run outside a DGGS. However, the results coming from these environmental models can be stored in a DGGS for efficient later use with other data.

This document specifies data models for a consistent set of common spatio-temporal classes, a DGGS core built on the common spatio-temporal classes, and a DGGS EAERS (equal-area Earth RS). The Common Spatio-temporal Classes, DGGS Core, and Equal-Area Earth DGGS packages each have their own conformance classes with their associated specifications and requirements.

The DGGS Core package is comprised of a RS, and functions for quantization, topological query and interoperability.

The DGGS Core RS is a RS using zonal identifiers with structured geometry located in its real world by coordinates in a base CRS. The DGGS Core RS is designed to support:

The RS in Equal-Area Earth DGGS is a specialization of the DGGS Core RS. It describes a RS, comprising:

This document does not prescribe any specific Earth surface model, base polyhedron or class of polyhedra, but is intended to allow for a range of options that produce DGGSs with compatible and interoperable functional characteristics.

Future additions to the OGC Topic 21 / ISO 19170 series are intended to cover:

Topic 21 - Discrete Global Grid Systems - Part 1 Core Reference system and Operations and Equal Area Earth Reference System

1.  Scope

This document supports the definition of:

2.  Conformance

This standard defines the conformance classes listed in tables Table 1Table 3

Table 1 — Conformance classes for Common Spatio-temporal Classes package

Conformance class Requirement tests
Temporal geometry and topology Annex A.1, Requirement test A.1
Temporal reference systems using period identifiers Annex A.1, Requirement test A.4
Spatial zone geometry and topology Annex A.1, Requirement test A.2
Spatial reference systems using zonal identifiers Annex A.1, Requirement test A.3, & Annex A.1, Requirement test A.5
Spatio-temporal zone geometry and topology Annex A.1, Requirement test A.1, & Annex A.1, Requirement test A.2
Spatio-temporal reference systems using zonal identifiers Annex A.1, Requirement test A.3, Annex A.1, Requirement test A.4, & Annex A.1, Requirement test A.5


Table 2 — Conformance classes for DGGS Core package

Conformance class Requirement tests
Spatial DGGS Core Annex A.1, Requirement test A.2, Annex A.1, Requirement test A.3, Annex A.1, Requirement test A.5, and
all Core requirements in Annex A.2.1, Requirement test A.6Annex A.2.2, Requirement test A.19.
Spatio-temporal DGGS Core Annex A.1, Requirement test A.1, Annex A.1, Requirement test A.2, Annex A.1, Requirement test A.3, Annex A.1, Requirement test A.4, Annex A.1, Requirement test A.5, and
all Core requirement tests in Annex A.2.1, Requirement test A.6Annex A.2.2, Requirement test A.19.


Table 3 — Categories of conformance for Equal-Area Earth DGGS package

Conformance class Requirement tests
Equal-Area Earth DGGS Annex A.1, Requirement test A.2, Annex A.1, Requirement test A.3, & Annex A.1, Requirement test A.5, and
all Core requirement tests in Annex A.2.1, Requirement test A.6Annex A.2.2, Requirement test A.19, and
all EAERS requirement tests in Annex A.3, Requirement test A.20Annex A.3, Requirement test A.29.


Conformance with this standard shall be checked using the relevant tests specified in Annex A (normative) of this document. The framework, concepts, and methodology for testing, and the criteria to be achieved to claim conformance are specified in the OGC Compliance Testing Policies and Procedures and the OGC Compliance Testing web site.

All requirements-classes and conformance-classes described in this document are owned by the standard(s) identified.

3.  Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

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

ISO: ISO 19107:2019, Geographic information — Spatial schema. International Organization for Standardization, Geneva (2019). https://www.iso.org/standard/66175.html

The following pair of OGC and ISO documents are identical in normative content:

Roger Lott: OGC 18-005r5, Topic 2 — Referencing by coordinates Corrigendum. Open Geospatial Consortium (2021). https://docs.ogc.org/as/18-005r5/18-005r5.html

ISO: ISO 19111:2019, Geographic information — Referencing by coordinates. International Organization for Standardization, Geneva (2019). https://www.iso.org/standard/74039.html

ISO: ISO 19112:2019, Geographic information — Spatial referencing by geographic identifiers. International Organization for Standardization, Geneva (2019). https://www.iso.org/standard/70742.html

The following pair of OGC and ISO documents are identical in normative content:

ISO: OGC 11-111r1, Topic 11 — Metadata. Open Geospatial Consortium (2016). http://www.iso.org/iso/home/store/catalogue_ics/catalogue_detail_ics.htm?csnumber=53798

ISO: ISO 19115-1:2014, Geographic information — Metadata — Part 1: Fundamentals. International Organization for Standardization, Geneva (2014). https://www.iso.org/standard/53798.html

The following pair of OGC and ISO documents are identical in normative content:

Simon Cox: OGC 10-004r3, Topic 20 — Observations and Measurements. Open Geospatial Consortium (2010). https://portal.ogc.org/files/?artifact_id=41579

ISO: ISO 19156:2011, Geographic information — Observations and measurements. International Organization for Standardization, Geneva (2011). https://www.iso.org/standard/32574.html

4.  Terms and definitions

This document uses the terms defined in OGC Policy Directive 49, which is based on the ISO/IEC Directives, Part 2, Rules for the structure and drafting of International Standards. In particular, the word “shall” (not “must”) is the verb form used to indicate a requirement to be strictly followed to conform to this standard and OGC documents do not use the equivalent phrases in the ISO/IEC Directives, Part 2.

This document also uses terms defined in the OGC Standard for Modular specifications (OGC 08-131r3), also known as the ‘ModSpec’. The definitions of terms such as standard, specification, requirement, and conformance test are provided in the ModSpec.

For the purposes of this document, the following additional terms and definitions apply.

This document uses the terms defined in Sub-clause 5.3 of OGC 06-121r9, which is based on the ISO/IEC Directives, Part 2, Rules for the structure and drafting of International Standards. In particular, the word “shall” (not “must”) is the verb form used to indicate a requirement to be strictly followed to conform to this standard.

4.1. boundary child ADMITTED compound CRS ADMITTED CRS ADMITTED reference frame ADMITTED DGGS ADMITTED dynamic CRS ADMITTED dynamic datum ADMITTED geodetic CRS ADMITTED geographic CRS ADMITTED global ADMITTED parent ADMITTED sibling ADMITTED spatio-temporal CRS ADMITTED static CRS ADMITTED static datum ADMITTED temporal CRS ADMITTED

set that represents the limit of an entity

Note 1 to entry: Boundary is most commonly used in the context of geometry, where the set is a collection of points or a collection of objects that represent those points. In other domains, the term is used metaphorically to describe the transition between an entity and the rest of its domain of discourse.

[SOURCE: ISO 19107:2019, Clause 3.6]

4.2. cell

<DGGS> spatial, spatio-temporal or temporal unit of geometry with dimension greater than 0, associated with a zone (Clause 4.52)

Note 1 to entry: All cells within a DGGS (Clause 4.13) share the dimensionality of the DGGS’s parent global (Clause 4.24) geometry. DGGS with dimensionality of 0, are not supported.

Note 2 to entry: Cells are the unit of geometry in a DGGS, and the geometry of the region of space-time occupied by a zone is a cell.

Note 3 to entry: While the terms cell and zone are often used interchangeably, strictly zone is the preferred term. Cell is entirely appropriate when specifically discussing a zone’s geometry or topology.

4.3. cell refinement

<DGGS> process of subdividing parent cells (Clause 4.33) into descendant child cells (Clause 4.4) using a specified refinement ratio (Clause 4.38) and suite of refinement strategies

Note 1 to entry: Iterative application of cell refinements creates a hierarchy of descendant discrete global grids (Clause 4.12).

Note 2 to entry: Cell refinement methods may result in child cells that each have a single parent or that have multiple parents.

4.4. child cell

<DGGS> immediate descendant of a parent cell (Clause 4.33)

Note 1 to entry: Child cells are either within a single parent cell or overlapped by multiple parent cells

4.5. class

description of a set of objects that share the same attributes, operations, methods, relationships, and semantics

Note 1 to entry: A class may use a set of interfaces to specify collections of operations it provides to its environment. The term was first used in this way in the general theory of object-oriented programming, and later adopted for use in this same sense in UML.

[SOURCE: ISO 19103:2015, Clause 4.7, modified — Note 1 to entry has been added from clause 4.2]

4.6. compound coordinate reference system

coordinate reference system (Clause 4.7) using at least two independent coordinate reference systems

Note 1 to entry: Coordinate reference systems are independent of each other if coordinate values in one cannot be converted or transformed into coordinate values in the other.

[SOURCE: ISO 19111:2019, Clause 3.1.3]

4.7. coordinate reference system

coordinate system that is related to an object by a datum (Clause 4.10)

Note 1 to entry: Geodetic and vertical datums are referred to as reference frames.

Note 2 to entry: For geodetic and vertical datums, the object will be the Earth. In planetary applications, geodetic and vertical reference frames may be applied to other celestial bodies.

[SOURCE: ISO 19111:2019, Clause 3.1.9]

4.8. coordinate system

set of mathematical rules for specifying how coordinates are to be assigned to points

[SOURCE: ISO 19111:2019, Clause 3.1.11]

4.9. data type

specification of a value (Clause 4.49) domain with operations allowed on values in this domain

Note 1 to entry: Data types include primitive predefined types and user-definable types. All instances of a data type lack identity.

Example

Integer, Real, Boolean, String, Date (conversion of a date into a series of codes).

[SOURCE: ISO 19103:2015, Clause 4.14, modified — Note 1 to entry has been added from ISO 19156:2011, Clause 4.3]

4.10. datum

parameter or set of parameters that realize the positions of the origin, the scale, and the orientation of a coordinate system (Clause 4.8)

[SOURCE: ISO 19111:2019, Clause 3.1.15]

4.11. datum ensemble

group of multiple realizations of the same terrestrial or vertical reference system that, for approximate spatial referencing purposes, are not significantly different

Note 1 to entry: Datasets referenced to the different realizations within a datum ensemble may be merged without coordinate transformation.

Note 2 to entry: ‘Approximate’ is for users to define but typically is in the order of under 1 decimetre but may be up to 2 metres.

Example

“WGS 84” as an undifferentiated group of realizations including WGS 84 (TRANSIT), WGS 84 (G730), WGS 84 (G873), WGS 84 (G1150), WGS 84 (G1674) and WGS 84 (G1762). At the surface of the Earth these have changed on average by 0.7 m between the TRANSIT and G730 realizations, a further 0.2 m between G730 and G873, 0.06 m between G873 and G1150, 0.2 m between G1150 and G1674 and 0.02 m between G1674 and G1762).

[SOURCE: ISO 19111:2019, Clause 3.1.16]

4.12. discrete global grid

<DGGS> set of cells (Clause 4.2) at the same refinement level (Clause 4.37), that uniquely and completely cover a globe (Clause 4.24)

Note 1 to entry: the set of cell zonal identifiers (Clause 4.50) comprising a discrete global grid form a single Zone Class with its associated refinement level.

Note 2 to entry: the configuration of the set of cells comprising a discrete global grid satisfy at least one grid constraint in the DGG_GridConstraint codelist.

4.13. discrete global grid system

integrated system comprising a hierarchy (Clause 4.26) of discrete global grids (Clause 4.12), spatio-temporal referencing (Clause 4.42) by zonal identifiers (Clause 4.50) and functions for quantization (Clause 4.36), zonal query (Clause 4.51), and interoperability (Clause 4.28)

4.14. duration

non-negative quantity of time equal to the difference between the final and initial instants (Clause 4.29) of a time interval (Clause 4.30)

Note 1 to entry: The duration is one of the base quantities in the International System of Quantities (ISQ) on which the International System of Units (SI) is based. The term “time” instead of “duration” is often used in this context and also for an infinitesimal duration.

Note 2 to entry: For the term “duration”, expressions such as “time” or “time interval” are often used, but the term “time” is not recommended in this sense and the term “time interval” is deprecated in this sense to avoid confusion with the concept of “time interval”.

Note 3 to entry: The exact duration of a time scale unit depends on the time scale used. For example, the durations of a year, month, week, day, hour or minute, may depend on when they occur [in a Gregorian calendar, a calendar month can have a duration of 28, 29, 30, or 31 days; in a 24-hour clock, a clock minute can have a duration of 59, 60, or 61 seconds, etc.]. Therefore, the exact duration can only be evaluated if the exact duration of each is known.

Note 4 to entry: This definition is closely related to NOTE 1 of the terminological entry “duration” in IEC 60050-113:2011, 113-01-13.

[SOURCE: ISO 8601-1:2019, Clause 3.1.1.8]

4.15. dynamic coordinate reference system

coordinate reference system (Clause 4.7) that has a dynamic reference frame (Clause 4.16)

Note 1 to entry: Coordinates of points on or near the crust of the Earth that are referenced to a dynamic coordinate reference system may change with time, usually due to crustal deformations such as tectonic motion and glacial isostatic adjustment.

Note 2 to entry: Metadata for a dataset referenced to a dynamic coordinate reference system should include coordinate epoch information.

[SOURCE: ISO 19111:2019, Clause 3.1.19]

4.16. dynamic reference frame

reference frame (Clause 4.10) in which the defining parameters include time evolution

Note 1 to entry: The defining parameters that have time evolution are usually a coordinate set.

[SOURCE: ISO 19111:2019, Clause 3.1.20]

4.17. error budget

<metric> statement of or methodology for describing the nature and magnitude of the errors which affect the results of a calculation

[SOURCE: ISO 19107:2019, Clause 3.35, modified — Note 1 to entry has been removed]

4.18. feature

abstraction of real-world phenomena

Note 1 to entry: A feature can occur as a type or an instance. In this document, feature instance is meant unless otherwise specified.

[SOURCE: ISO 19101-1:2014, Clause 4.1.11, modified — Note 1 to entry has been added from ISO 19156:2011, Clause 4.6, and modified]

4.19. feature type

class (Clause 4.5) of features (Clause 4.18) having common characteristics

[SOURCE: ISO 19156:2011, Clause 4.7]

4.20. geodetic coordinate reference system

three-dimensional coordinate reference system (Clause 4.7) based on a geodetic reference frame and having either a three-dimensional Cartesian or a spherical coordinate system

Note 1 to entry: In this document a CRS based on a geodetic reference frame and having an ellipsoidal coordinate system is geographic.

[SOURCE: ISO 19111:2019, Clause 3.1.31]

4.21. geographic coordinate reference system

coordinate reference system (Clause 4.7) that has a geodetic reference frame and an ellipsoidal coordinate system

[SOURCE: ISO 19111:2019, Clause 3.1.35]

4.22. geographic identifier

spatial reference (Clause 4.41) in the form of a label or code that identifies a location (Clause 4.31)

Example

“Spain” is an example of a label (country name); “SW1P 3AD” is an example of a code (postcode).

[SOURCE: ISO 19112:2019, Clause 3.1.2]

4.23. geometric primitive

geometric object representing a single, connected, homogeneous (isotropic) element of space

Note 1 to entry: Geometric primitives are non-decomposed objects that present information about geometric configuration. They include points, curves, surfaces, and solids. Many geometric objects behave like primitives (supporting the same interfaces defined for geometric primitives) but are actually composites composed of some number of other primitives. General collections may be aggregates and incapable of acting like a primitive (such as the lines of a complex network, which is not connected and thus incapable of being traceable as a single line). By this definition, a geometric primitive is topological open, since the boundary (Clause 4.1) points are not isotropic to the interior points. Geometry is assumed to be closed. For points, the boundary is empty.

[SOURCE: ISO 19107:2019, Clause 3.50]

4.24. globe

<DGGS> region of space-time enclosing a celestial body

Note 1 to entry: In this document globe is used in its most general form to refer to any celestial body or region of space-time enclosing a celestial body that may be referenced by a DGGS (Clause 4.13). When a specific body, such as the Earth is referred to, an explicit term is used.

4.25. grid

network composed of two or more sets of curves in which the members of each set intersect the members of the other sets in an algorithmic way

Note 1 to entry: The curves partition a space into grid cells.

[SOURCE: ISO 19123:2005, Clause 4.1.23]

4.26. hierarchy

<DGGS> organization and ranking of successive levels of cell refinement (Clause 4.3) of discrete global grids (Clause 4.12)

4.27. initial discrete global grid

<DGGS> discrete global grid tessellation created by circumscribing a defined path along the chosen surface model of the Earth between the vertices of the scaled base unit polyhedron

4.28. interoperability

capability to communicate, execute programmes, or transfer data among various functional units in a manner that requires the user to have little or no knowledge of the unique characteristics of those units

Note 1 to entry: in this document interoperability specifically refers to functions that initiate and process transfers of data from a DGGS (Clause 4.13).

[SOURCE: ISO/IEC 2382:2015, Clause 2121317, modified — The original domain and Notes to Entry have been deleted. A Note 1 to entry has been added.]

4.29. instant

<DGGS> temporal geometry primitive representing a point in time

Note 1 to entry: On temporal coordinate systems (Clause 4.46) as specified in ISO 19107:2019, the temporal geometric primitives (Clause 4.23) instant and interval (Clause 4.30) are the equivalent of points and lines as specified in ISO 19107:2019.

4.30. interval

<DGGS> temporal geometry primitive representing a line in time

Note 1 to entry: On temporal coordinate systems (Clause 4.46) as specified in (ISO 19107:2019), the temporal geometric primitives (Clause 4.23) instant (Clause 4.29) and interval are the equivalent of points and lines as specified in ISO 19107:2019.

4.31. location

particular place or position

Note 1 to entry: A location identifies a geographic place.

Note 2 to entry: In the context of DGGS (Clause 4.13), locations have dimension greater than one, and so are not points.

Example

“Madrid”, “SW1P 3AD”.

[SOURCE: ISO 19112:2019, Clause 3.1.3, modified — Note two has been added and an additional example provided]

4.32. observation

act of measuring or otherwise determining the value (Clause 4.49) of a property

[SOURCE: ISO 19156:2011, Clause 4.11]

4.33. parent cell

<DGGS> cell (Clause 4.2) in a higher refinement level of discrete global grid with immediate descendants

Note 1 to entry: parent cells either overlap or contain their child cells (Clause 4.4).

4.34. period

<DGGS> particular era or span of time

Note 1 to entry: Periods are intervals (Clause 4.30) named with a period identifier (Clause 4.35)

4.35. period identifier

<DGGS> temporal reference in the form of a label or code that identifies a period (Clause 4.34)

Note 1 to entry: Period identifiers are the temporal equivalent of geographic identifiers (Clause 4.22) as specified in ISO 19112:2019

4.36. quantization

<DGGS> function assigning data from external sources to cell values

4.37. refinement level

<DGGS> numerical order of a discrete global grid (Clause 4.12) in the tessellation sequence

Note 1 to entry: The tessellation with the smallest number of cells has a refinement level = 0.

4.38. refinement ratio

<DGGS> ratio of the number of child cells (Clause 4.4) to parent cells (Clause 4.33)

Note 1 to entry: A positive integer ratio n refinement of DGGS (Clause 4.13) parent cells yield n times as many child cells as parent cells.

Note 2 to entry: For a two-dimensional DGGS (as defined for EAERS in this document) this is the surface area ratio.

Note 3 to entry: In DGGS literature [2] the term aperture has been used instead of refinement ratio. Refinement ratio is preferred because it is clearer in meaning to audiences outside the early DGGS community.

4.39. sibling cell

<DGGS> cell (Clause 4.2) in a discrete global grid with the same parent cell (Clause 4.33)

Note 1 to entry: all the child cells (Clause 4.4) of a parent cell are each-others’ sibling cells.

4.40. simple

<topology, geometry> homogeneous (all points have isomorphic neighbourhoods) and with a simple boundary (Clause 4.1)

Note 1 to entry: The interior is everywhere locally isomorphic to an open disc in a Euclidean coordinate space of the appropriate dimension Dn = {P|‖P‖ < 1.0}. The boundary is a dimension one smaller. This essentially means that the object does not intersect nor touch itself. Generally used for a curve that does not cross not touch itself with the possible exception of boundary points. Simple closed curves are isomorphic to a circle.

[SOURCE: ISO 19107:2019, Clause 3.84]

4.41. spatial reference

description of position in the real world

Note 1 to entry: This may take the form of a label, code or coordinate tuple.

[SOURCE: ISO 19111:2019, Clause 3.1.56]

4.42. spatio-temporal reference

system for identifying position in the real world that may include time

Note 1 to entry: This may take the form of a label, code or coordinate tuple.

4.43. spatio-temporal coordinate reference system

compound coordinate reference system (Clause 4.6) in which one constituent coordinate reference system (Clause 4.7) is a spatial coordinate reference system and one is a temporal coordinate reference system (Clause 4.47)

[SOURCE: ISO 19111:2019, Clause 3.1.59]

4.44. static coordinate reference system

coordinate reference system (Clause 4.7) that has a static reference frame (Clause 4.45)

Note 1 to entry: Coordinates of points on or near the crust of the Earth that are referenced to a dynamic coordinate reference system do not change with time.

Note 2 to entry: Metadata for a dataset referenced to a static coordinate reference system does not require coordinate epoch information.

[SOURCE: ISO 19111:2019, Clause 3.1.61]

4.45. static reference frame

reference frame (Clause 4.10) in which the defining parameters exclude time evolution

[SOURCE: ISO 19111:2019, Clause 3.1.62]

4.46. temporal coordinate system

<geodesy> one-dimensional coordinate system where the axis is time

[SOURCE: ISO 19111:2019, Clause 3.1.64]

4.47. temporal coordinate reference system

coordinate reference system (Clause 4.7) based on a temporal datum

[SOURCE: ISO 19111:2019, Clause 3.1.63]

4.48. tessellation

partitioning of a space into a set of conterminous subspaces having the same dimension as the space being partitioned

Note 1 to entry: A tessellation composed of congruent regular polygons or polyhedra is a regular tessellation. One composed of regular, but non-congruent polygons or polyhedra is a semi-regular tessellation. Otherwise the tessellation is irregular. Tessellations on curved surfaces cannot be congruent, so all tessellations in DGGS (Clause 4.13) are either semi-regular or irregular.

Example

Graphic examples of tessellations may be found in Figures 11, 13, 20, and 22 of [ISO19123].

[SOURCE: ISO 19123:2005, Clause 4.1.39, modified — Note 1 to entry has been modified and new notes to entry have been added.]

4.49. value

element of a type domain

Note 1 to entry: A value considers a possible state of an object within a class (Clause 4.5) or type (domain).

Note 2 to entry: A data value is an instance of a datatype, a value without identity.

Note 3 to entry: A value can use one of a variety of scales including nominal, ordinal, ratio and interval, spatial and temporal. Primitive datatypes can be combined to form aggregate datatypes with aggregate values, including vectors, tensors and images.

[SOURCE: ISO 19156:2011, Clause 4.18]

4.50. zonal identifier

<DGGS> spatio-temporal reference (Clause 4.42) in the form of a label or code that identifies a zone (Clause 4.52)

Note 1 to entry: A zonal identifier may be a geographic identifier (Clause 4.22), period identifier (Clause 4.35), or a compound of the two.

Note 2 to entry: A zone’s ZonalIdentifier provides the coordinates of a representative position for the zone, and spatio-temporal feature (Clause 4.18) geometry is represented by sets of ZonalIdentifiers.

4.51. zonal query

<DGGS> geometry or topology function using a cell’s zonal identifiers (Clause 4.50) to specify geometry

Note 1 to entry: ISO 19107:2019 specifies a suite of geometry and topology functions in the Query2D and Query3D classes, where geometry elements used in each function’s parameters are described by sets of coordinates. In DGGS (Clause 4.13) all geometry can be referenced as sets of cells (Clause 4.2) represented solely by a list (or set) of their zonal identifiers. This document specifies ZoneQuery to implement the operations in both Query2D and Query3D using zonal identifiers to reference each operation’s source and target geometry.

4.52. zone

<DGGS> particular region of space-time

Note 1 to entry: The primitives of zone are spatial location (Clause 4.31) and temporal period (Clause 4.34).

Note 2 to entry: A zone may be either a single zonal primitive or a compound zone comprising one spatial location and one temporal period. Zones can be regions of space-time associated with any celestial body.

Note 3 to entry: Zones are the primary container for storing and retrieving data within a DGGS implementation. DGGSs reference zones by their zonal identifier (Clause 4.50), for instance in databases or through tile nomenclature.

Note 4 to entry: Each zone’s geometry is represented by a cell (Clause 4.2).

5.  Conventions

5.1.  Abbreviated terms

DE-9IM

Dimensionally Extended 9-Intersection Model

EAERS

equal-area Earth RS

EC

earth-centered

ECEF

earth-centered earth fixed

GEM

Geodesic Elevation Model

GIS

geographic information system

GUID

globally unique identifier

HPC

high-performance computing

HPD

high-performance data

ICT

information and communications technology

ISEA

Icosahedral Snyder Equal Area

ISEA3H

Icosahedral Snyder Equal Area Aperture 3 Hexagon

ISO

International Organization for Standardization

OGC

Open Geospatial Consortium

OWS

OGC Web-Service

QTM

Quaternary Triangular Mesh

rHEALPix

rearranged Hierarchical Equal Area isoLatitude Pixelization

RS

reference system

UML

Unified Modeling Language

URI

Uniform Resource Identifier

5.2.  Universal Resource Identifiers

The normative provisions in this specification are denoted by the URI:

http://www.opengis.net/spec/dggs/2.0

All requirements and conformance tests that appear in this document denoted by partial URIs are relative to this base.

5.3.  Unified Modelling Language notation

In this document, the conceptual schema for describing DGGSs are presented in the UML. ISO 19103:2015 presents the specific profile of UML used in this document.

The UML diagrams in this document refer to classifiers in five other standards. Each standard has been assigned a colour that is used consistently across all UML diagrams. Each diagram has a key listing the standards referred to in that diagram and their colours. Interface names in the figure have the structure <module-name>::<interface-name>. For reference, Table 1 lists all the module names and the standard they belong to. Both colour and module name can be used as quick reference to a classifier’s standard.

5.4.  Naming conventions

Where possible, when a classifier represents the common behaviour of a set of defined things from the terms defined in Clause 3, the UML classifier will generally use the defined terms as its name. Since classifier names are capitalized and contain no space, and the defined term may contain several words, the classifier name will separate words using upper-camel-case concatenations (no spaces but each word beginning with a capital with all other letters in lowercase). Similarly, the name may be some simplified key phrase. This “UpperCamelCase” rule is generally followed but may be violated if clarity or consistency with other standards is improved by minor violations. For example:

  • Zone identifier values are represented by the interface ZonalIdentifier or stored using the datatype DirectPosition defined in ISO 19107:2019.

  • Instances of primitives will realize the interface Primitive in the package Common Spatio-temporal Classes and other interfaces for their specific dimension and interpolation mechanism. For example, Point, Instant, Interval, Line, NodeT, LocationS.

  • Any classifier name referenced from another standard retains its original format.

Classifier names for attributes and operations in the UML models may similarly use key phrases in lowerCamelCase (same as UpperCamelCase, but the first word begins in a lowercase letter). For example: parent; child; parentOf; childOf and relatePosition are all used as operation names.

Module and package names can contain spaces. In some situations, a phrase that has an abbreviation is used in its unabbreviated form as a package name. Where a package or module is referred to in the text, both the capitalisation and unabbreviated form are preserved. This distinguishes them from a phrase in general use. For example: DGGS Equal-Area Earth Reference System; Zone and Temporal Geometry; and Reference System defined in this standard and Coordinate Reference Systems defined in ISO 19111:2019.

In summary, the use of capitals for a term in the general text indicates a reference to a classifier from the UML

5.5.  Attribute and association role status

In this document, conceptual schema in Clauses 6–8 are defined by tables. In these tables:

  • attributes and association roles are given an Obligation status:

    • M: mandatory — this attribute or association role shall be supplied.

    • C: conditional — this attribute or association role shall be supplied if the condition (given in the description) is true. It may be supplied if the condition is false.

    • O: optional — this attribute or association role may be supplied.

  • the Maximum Occurrence column in the tables indicates the maximum number of occurrences of attribute values that are permissible, with * indicating no upper limit.

  • non-navigable associations are not included in the UML diagrams or tables.

The tables provide a summary of the UML diagrams. In particular, association roles, attributes, operations, and constraints that are inherited from another class unchanged are not described in the tables. In the event of any discrepancies between the UML diagrams and text, the UML shall prevail.

6.  DGGS Specification Overview

6.1.  Package overview

The specification for DGGSs is described in this document in the form of a UML model with supplementary defining tables and text. The UML data model is organised into three primary packages. The Common Spatio-temporal Classes package contains two UML sub-packages, DGGS Core contains four UML sub-packages, and DGGS Equal-Area Earth Reference System package is a single UML package, as shown in Figure 2.

  • Common Spatio-temporal Classes package contains

    • Zone and Temporal Geometry package, comprising temporal and spatio-temporal primitives for geometry and topology,

    • Zone, Identifier and RS package, comprising temporal and spatio-temporal RS using identifiers and their primitives.

  • DGGS Core package contains:

    • Core RS using zonal identifiers with structured geometry package,

    • Core Quantisation Functions package,

    • Core Query Functions package,

    • Core Interoperation Functions package.

  • Equal-Area Earth DGGS package.

In Figure 2, each box represents a package and contains the package name. Each arrowed line shows the normative dependency of one package upon another package (at the head of the arrow). The Common Spatio-temporal Classes, DGGS Core and Equal-Area Earth DGGS packages dependent on packages in five other ISO standards.

Figure 2 — DGGS Package Diagram

Packages are grouped in a hierarchy of sub-packages, with modules containing interfaces at the leaves of the hierarchy. In the UML diagrams that follow, interface names are often shown as <module-name>::<interface-name>. For reference, Table 4 lists all the module names that are referred in the diagrams and names the standard they come from.

Table 4 — Module names used in UML diagrams in this document

Standard name

Module name
ISO 19107:2019 Spatial Schema Ed 2Edge
Geometry
Node
Topology
ISO 19111:2019 Referencing by Coordinates Ed 3Common Classes
Coordinates
Coordinate Operations
Coordinate Reference System
Coordinate Systems
ISO 19112:2019 Spatial referencing by geographic identifier Ed 2ISO 19112 Edition 2
ISO 19115-1:2014 Metadata Ed 1Reference system information
ISO 19156:2011 Observation and Measurements Ed 1Observation
ISO 19170-1 Discrete Global Grid Systems Ed 1Common Spatio-temporal ClassesTemporal Geometry and Topology
Zonal Geometry and Topology
Temporal RS using Identifiers
Spatial Location
Zonal RS using Identifiers
DGGS CoreCore RS using Zonal Identifiers with Structured Geometry
Core Quantization Functions
Core Topological Query Functions
Core Interoperation Functions
Interoperation Query
Interoperation Broadcast
Equal-Area Earth DGGSEqual-Area Earth RS
Equal-Area Tessellation
Equal-Area Cell

Conformance classes for the modules in the Common Spatio-temporal Classes, DGGS Core, and Equal-Area Earth DGGS packages are described in Annex A.

One product conformance class is also defined for an Equal-Area Earth DGGS product, that brings modules together as a system.

7.  Common Spatio-temporal Classes Package

7.1.  Common Spatio-temporal Classes overview

This clause specifies the common spatio-temporal classes to support temporal and spatio-temporal geometry, topology, zones, zonal identifiers, zonal query, and RSs using temporal or zonal identifiers.

These classes are defined here in such a way that they can be used in any context which requires an internally consistent set of temporal and spatio-temporal classes for use with spatial classes from ISO 19107, 19111 and 19112. They are further specialised in the DGGS Core for use in DGGS. In this restricted model for spatio-temporal systems, the spatio-temporal scope is constrained to spatial classes that are invariant through all time, and to temporal classes that are invariant throughout space.

The Common Spatio-temporal Classes are organized into two packages with five modules:

  1. Temporal and Zonal Geometry package comprises:

    1. Temporal Geometry and Topology module

    2. Zonal Geometry and Topology module

  2. RS using Temporal and Zonal Identifiers package comprises:

    1. Spatial Location module

    2. Temporal RS using Identifiers module

    3. Zonal RS using Identifiers module

In each package separate spatial and temporal classes are defined first, followed by spatio-temporal classes that bring temporal and spatial classes together.

7.2.  Temporal and Zonal Geometry package

7.2.1.  Temporal Geometry and Topology module

7.2.1.1.  Context and data model

Temporal geometry is geometry constrained to one of the temporal coordinate systems, defined by TemporalCS in ISO 19111:2019. Temporal geometry primitives instant and interval implement the temporal analogues of point and line respectively in ISO 19107:2019. All geometry has topology, and the temporal topology primitives nodeT and edgeT implement the temporal analogues of node and edge respectively. These are shown in Figure 3.

Figure 3 — Primitives of Temporal Geometry and Topology

Temporal interfaces paralleling the spatial geometry and topology interface structure are built from these temporal primitives. Each temporal interface has the same meaning and semantics as their equivalent spatial interface, with the constraint that all temporal interfaces are constrained to the same coordinate system as their temporal primitives. Figure 4 shows the spatial classes on the left and their temporal equivalents on the right.

Figure 4 — ISO 19107:2019 Context for Temporal Geometry and Topology

7.2.1.2.  Defining tables

  1. Table 5 — Elements of Temporal Geometry and Topology::Duration

  2. Table 6 — Elements of Temporal Geometry and Topology::EdgeT

  3. Table 7 — Elements of Temporal Geometry and Topology::Instant

  4. Table 8 — Elements of Temporal Geometry and Topology::Interval

  5. Table 9 — Elements of Temporal Geometry and Topology::NodeT

  6. Table 10 — Elements of Temporal Geometry and Topology::TemporalGeometricCollection

  7. Table 11 — Elements of Temporal Geometry and Topology::TemporalGeometricComplex

  8. Table 12 — Elements of Temporal Geometry and Topology::TemporalGeometricPrimitive

  9. Table 13 — Elements of Temporal Geometry and Topology::TemporalGeometry

  10. Table 14 — Elements of Temporal Geometry and Topology::TemporalTopologicalComplex

  11. Table 15 — Elements of Temporal Geometry and Topology::TemporalTopologicalPrimitive

  12. Table 16 — Elements of Temporal Geometry and Topology::TemporalTopology

Table 5 — Elements of Temporal Geometry and Topology::Duration

Name:

Duration

Definition:

Duration implements Length on a Temporal Coordinate System.

Stereotype:

Union

Abstract:

true

Associations:

(none)

Public attributes:

Name

Definition

Derived

Obligation

Maximum occurrence

Data type

durationLengthDT

Length of time for Duration of type DateTime.

C

1

DateTime

durationLengthI

Length of time for Duration of type Integer count.

C

1

Integer

durationLengthM

Length of time for Duration of type Real measure.

C

1

Real

durationType

Type of unit of measure for time.

true

M

1

CoordinateDataType (code list)

Constraints:

(none)


Table 6 — Elements of Temporal Geometry and Topology::EdgeT

Name:

EdgeT

Definition:

Topological temporal edge,
one-dimensional topological primitive.

Stereotype:

Interface

Inheritance from:

Edge, TemporalTopologicalPrimitive

Abstract:

true

Associations:

(none)

Public attributes:

(none)

Constraints:

(none)


Table 7 — Elements of Temporal Geometry and Topology::Instant

Name:

Instant

Definition:

Instant implements Point geometry on a Temporal Coordinate System.

Stereotype:

Interface

Inheritance from:

TemporalGeometricPrimitive, Point

Abstract:

true

Associations:

(none)

Public attributes:

(none)

Constraints:

self.type = point


Table 8 — Elements of Temporal Geometry and Topology::Interval

Name:

Interval

Definition:

Interval implements Line geometry on a Temporal Coordinate System.

Stereotype:

Interface

Inheritance from:

Line, TemporalGeometricPrimitive

Abstract:

true

Associations:

(none)

Public attributes:

(none)

Constraints:

(none)


Table 9 — Elements of Temporal Geometry and Topology::NodeT

Name:

NodeT

Definition:

Topological temporal node,
zero-dimensional topological primitive, its boundary being empty.

Stereotype:

Interface

Inheritance from:

Node, TemporalTopologicalPrimitive

Abstract:

true

Associations:

(none)

Public attributes:

(none)

Constraints:

(none)


Table 10 — Elements of Temporal Geometry and Topology::TemporalGeometricCollection

Name:

TemporalGeometricCollection

Definition:

Temporal Geometric Collection implements geometric Collection for Temporal Geometry.

Stereotype:

Interface

Inheritance from:

TemporalGeometry

Generalization of:

TemporalGeometricComplex

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

TemporalGeometry (feature type)

C

*

element

Public attributes:

(none)

Constraints:

(none)


Table 11 — Elements of Temporal Geometry and Topology::TemporalGeometricComplex

Name:

TemporalGeometricComplex

Definition:

Temporal Geometric Complex implements geometric Complex for Temporal Geometry.

Stereotype:

Interface

Inheritance from:

TemporalGeometricCollection

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

TemporalGeometricPrimitive (feature type)

C

*

element

TM_GeometricPrimitive (feature type)

C

*

element

TemporalTopologicalComplex (feature type)

C

1

topology

Public attributes:

(none)

Constraints:

(none)


Table 12 — Elements of Temporal Geometry and Topology::TemporalGeometricPrimitive

Name:

TemporalGeometricPrimitive

Definition:

Temporal Geometric Primitive implements geometric Primitive for Temporal Geometry.

Stereotype:

Interface

Inheritance from:

TemporalGeometry, Primitive

Generalization of:

Instant, Interval

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

TemporalTopologicalPrimitive (feature type)

C

*

topology

Public attributes:

Name

Definition

Derived

Obligation

Maximum occurrence

Data type

spatialDimension

Dimension of its spatial geometry component.

M

1

Integer

temporalDimension

Dimension of its temporal geometry component.

M

1

Integer

Constraints:

(none)


Table 13 — Elements of Temporal Geometry and Topology::TemporalGeometry

Name:

TemporalGeometry

Definition:

Temporal Geometry implements 1D Geometry on a Temporal Coordinate System.

Stereotype:

Interface

Inheritance from:

Geometry, ZoneSimpleGeometry

Generalization of:

TemporalGeometricCollection, TemporalGeometricPrimitive

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

TemporalTopology (feature type)

C

1

topology

Public attributes:

(none)

Constraints:

self.coordinateDimension <= 1

self.rsid.CoordinateSystem = TemporalCS

self.spatialDimension.isEmpty = True

self.type.in{point,line} = True


Table 14 — Elements of Temporal Geometry and Topology::TemporalTopologicalComplex

Name:

TemporalTopologicalComplex

Definition:

Temporal Topological Complex implements topological Complex for Temporal Topology.

Stereotype:

Interface

Inheritance from:

TemporalTopology

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

TemporalTopologicalPrimitive (feature type)

C

1

element

TemporalGeometricComplex (feature type)

C

1

geometry

Public attributes:

(none)

Constraints:

(none)


Table 15 — Elements of Temporal Geometry and Topology::TemporalTopologicalPrimitive

Name:

TemporalTopologicalPrimitive

Definition:

Temporal Topological Primitive implements topological Primitive for Temporal Topology.

Stereotype:

Interface

Inheritance from:

TemporalTopology

Generalization of:

EdgeT, NodeT

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

TemporalGeometricPrimitive (feature type)

C

1

geometry

Public attributes:

(none)

Constraints:

(none)


Table 16 — Elements of Temporal Geometry and Topology::TemporalTopology

Name:

TemporalTopology

Definition:

Temporal Topology implements 1D Topology for Temporal Geometry.

Stereotype:

Interface

Inheritance from:

Topology, ZoneSimpleTopology

Generalization of:

TemporalTopologicalComplex, TemporalTopologicalPrimitive

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

TemporalGeometry (feature type)

C

1

geometry

TemporalGeometry (feature type)

C

1

time

Public attributes:

(none)

Constraints:

(none)


The following requirement applies:

Requirement 1

www.opengis.net/spec/DGGS/2.0/req/cc/temporal/geometry

The common classes for temporal geometry and topology shall conform to the data model in Figure 3 and Figure 4 and defining tables in Table 5Table 16. .


7.2.2.  Zonal geometry and topology module

7.2.2.1.  Context and data model

Referring to Figure 5, ZoneGeometry is either a primitive of ZoneSingleGeometry or a compound of two ZoneSingleGeometry primitives — one spatial and one temporal.

Zones exhibit topology of the same spatio-temporal dimension as their geometry.

Figure 5 — Components of Zonal Geometry and Topology module

7.2.2.2.  Defining tables

  1. Table 17 — Elements of Zonal Geometry and Topology::ZoneCompoundGeometry

  2. Table 18 — Elements of Zonal Geometry and Topology::ZoneCompoundTopology

  3. Table 19 — Elements of Zonal Geometry and Topology::ZoneGeometry

  4. Table 20 — Elements of Zonal Geometry and Topology::ZoneSimpleGeometry

  5. Table 21 — Elements of Zonal Geometry and Topology::ZoneSimpleTopology

  6. Table 22 — Elements of Zonal Geometry and Topology::ZoneTopology

Table 17 — Elements of Zonal Geometry and Topology::ZoneCompoundGeometry

Name:

ZoneCompoundGeometry

Definition:

ZoneCompoundGeometry is a Compound of two ZoneSimpleGeometry elements, comprising one one-, two- or three-dimensional spatial geometry and one one-dimensional temporal geometry.
NOTE This is analogous to an ISO 19111 Compound set of orthogonal space time axes comprising a set of orthogonal spatial axes and one temporal axis orthogonal to the spatial axes. ZoneCompoundGeometry has ZoneCompoundTopology.

Stereotype:

Interface

Inheritance from:

ZoneGeometry

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

ZoneSimpleGeometry (feature type)

M

2

componentPrimitive

ZoneCompoundTopology (feature type)

C

1

topology

Public attributes:

(none)

Constraints:

count(Geometry)=count(TemporalGeometry)=1

self.dimension=dimension(Geometry)+1


Table 18 — Elements of Zonal Geometry and Topology::ZoneCompoundTopology

Name:

ZoneCompoundTopology

Definition:

ZoneCompoundTopology exhibits both spatial topology with respect to the spatial component of its geometry and temporal topology with respect to the temporal component of its geometry.

Stereotype:

Interface

Inheritance from:

ZoneTopology

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

ZoneSimpleTopology (feature type)

M

2

componentPrimitive

ZoneCompoundGeometry (feature type)

C

1

geometry

Public attributes:

(none)

Constraints:

(none)


Table 19 — Elements of Zonal Geometry and Topology::ZoneGeometry

Name:

ZoneGeometry

Definition:

ZoneGeometry is a ZoneSimpleGeometry or a ZoneCompoundGeometry. It is the root geometry for all spatio-temporal geometry.

Stereotype:

Interface

Generalization of:

ZoneCompoundGeometry, ZoneSimpleGeometry

Abstract:

true

Associations:

(none)

Public attributes:

Name

Definition

Derived

Obligation

Maximum occurrence

Data type

spatialDimension

Topological dimension of the spatial geometry component.
NOTE For geometries on the surface of ellipsoids, the spatial dimension is 3, and the topological dimension is 2.

M

1

Integer

temporalDimension

Topological dimension of the temporal geometry component.

M

1

Integer

topologicalDimension

Sum of dimensions of topological primitives.

M

1

Integer

Constraints:

(none)


Table 20 — Elements of Zonal Geometry and Topology::ZoneSimpleGeometry

Name:

ZoneSimpleGeometry

Definition:

ZoneSimpleGeometry is a one-, two- or three-dimensional spatial geometry that is invariant over all time, OR a one-dimensional temporal geometry invariant over all space. A ZoneSimpleGeometry has topology appropriate for its geometry.

Stereotype:

Interface

Inheritance from:

ZoneGeometry

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

Topology (feature type)

C

1

topology

Public attributes:

(none)

Constraints:

(none)


Table 21 — Elements of Zonal Geometry and Topology::ZoneSimpleTopology

Name:

ZoneSimpleTopology

Definition:

ZoneSimpleTopology is a one-, two- or three-dimensional spatial topology that is invariant over all time, OR a one-dimensional temporal topology that is invariant over all space.

Stereotype:

Interface

Inheritance from:

ZoneTopology

Abstract:

true

Associations:

(none)

Public attributes:

(none)

Constraints:

(none)


Table 22 — Elements of Zonal Geometry and Topology::ZoneTopology

Name:

ZoneTopology

Definition:

ZoneTopology is a ZoneSimpleTopology or a ZoneCompoundTopology

Stereotype:

Interface

Generalization of:

ZoneCompoundTopology, ZoneSimpleTopology

Abstract:

true

Associations:

(none)

Public attributes:

(none)

Constraints:

(none)


The following requirement applies:

Requirement 2

www.opengis.net/spec/DGGS/2.0/req/cc/zone/geometry

The common classes for zonal geometry and topology shall conform to the data model in Figure 5 and defining tables in Table 17Table 22. .


7.3.  Temporal and Zonal RS using Identifiers package

7.3.1.  Spatial Location module

7.3.1.1.  Context and data model

ISO 19112:2019 describes spatial refencing by geographic identifiers, locations and location classes. The LocationS interface is a specialisation of the Location interface from ISO 19112:2019. See Figure 6. In the next section the Period interface is introduced as the temporal equivalent of LocationS.

Figure 6 — Context for LocationS

7.3.1.2.  Defining tables

  1. Table 23 — Elements of Spatial Location::LocationS

Table 23 — Elements of Spatial Location::LocationS

Name:

LocationS

Definition:

Particular place or position.
NOTE unlike a Location as specified in (<<ISO19112>>), all LocationS are owned and defined by their ReferenceSystem and not by an independent authority.

Stereotype:

Interface

Inheritance from:

Location, ZonePrimitive

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

LocationS (feature type)

C

*

childOf

LocationS (feature type)

C

*

parentOf

Public attributes:

Name

Definition

Derived

Obligation

Maximum occurrence

Data type

coordinateTuple

Point within the extent of the spatial location.

M

3

DirectPosition (data type)

extent

Spatial extent of the location.

true

M

1

EX_Extent (data type)

identifier

Identifier of the spatial location.

M

1

GeographicIdentifier (data type)

Constraints:

self.dimension > 0


The following requirement applies:

Requirement 3

www.opengis.net/spec/DGGS/2.0/req/cc/spatial/location

The common classes for spatial location shall conform to the data model in Figure 6 and defining table in Table 23.


7.3.2.  Temporal RS using Identifiers module

7.3.2.1.  Context and data model

Semantically, the terms period and zone are defined as the temporal and spatio-temporal equivalents of a location. These are represented in the data model by the interfaces Period and Zone.

Referring to Figure 7 showing the spatial classes on the left and the temporal classes on the right, it is noted that Period is augmented by:

  • PeriodIdentifier data-type as the temporal equivalent of GeographicIdentifier,

  • Period interface as the temporal equivalent of LocationS, see Figure 6,

  • PeriodClass interface as the temporal equivalent of LocationClass, and

  • TemporalReferenceSystemusingPeriodIdentifiers interface as the temporal equivalent of SpatialReferenceusingGeographicIdentifiers.

Figure 7 — Context for Temporal RS using Identifiers module

7.3.2.2.  Defining tables

  1. Table 24 — Elements of Temporal RS using Identifiers::Period

  2. Table 25 — Elements of Temporal RS using Identifiers::PeriodClass

  3. Table 26 — Elements of Temporal RS using Identifiers::PeriodIdentifier

  4. Table 27 — Elements of Temporal RS using Identifiers::TemporalReferenceSystemUsingPeriodIdentifiers

Table 24 — Elements of Temporal RS using Identifiers::Period

Name:

Period

Definition:

Particular time span or era between two instants.

Stereotype:

Interface

Inheritance from:

ZonePrimitive

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

Period (feature type)

C

*

childOf

Period (feature type)

C

*

parentOf

Public attributes:

Name

Definition

Derived

Obligation

Maximum occurrence

Data type

begin

Instant at the beginning of the period.

true

M

1

DirectPosition (data type)

coordinateTuple

Position within the extent of the period.

M

1

DirectPosition (data type)

end

Instant at the end of the period.

true

M

1

DirectPosition (data type)

extent

Temporal extent of the period.

true

M

1

EX_TemporalExtent

identifier

Identifier of the period.

M

1

PeriodIdentifier (data type)

Constraints:

(none)


Table 25 — Elements of Temporal RS using Identifiers::PeriodClass

Name:

PeriodClass

Definition:

Categorization of Periods.

Stereotype:

Interface

Inheritance from:

ZoneClassPrimitive

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

PeriodClass (feature type)

M

1

childOf

TM_OrdinalReferenceSystem (feature type)

M

*

incorporatedIn

PeriodClass (feature type)

M

1

parentOf

Public attributes:

(none)

Constraints:

(none)


Table 26 — Elements of Temporal RS using Identifiers::PeriodIdentifier

Name:

PeriodIdentifier

Definition:

Temporal reference in the form of a label or code that identifies a period.

Stereotype:

DataType

Inheritance from:

ZonalIdentifierPrimitive

Abstract:

true

Associations:

(none)

Public attributes:

(none)

Constraints:

(none)


Table 27 — Elements of Temporal RS using Identifiers::TemporalReferenceSystemUsingPeriodIdentifiers

Name:

TemporalReferenceSystemUsingPeriodIdentifiers

Definition:

A temporal RS based on period identifiers.

Stereotype:

Interface

Inheritance from:

RSUsingZonalIdentifiersPrimitive

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

Period (feature type)

M

*

component

Public attributes:

(none)

Constraints:

(none)


The following requirement applies:

Requirement 4

www.opengis.net/spec/DGGS/2.0/req/cc/temporal/rsupi

_The common classes for reference systems using period identifiers shall conform to the data model in Figure 7 and defining tables in Table 24Table 27.


7.3.3.  Zonal RS using Identifiers module

7.3.3.1.  Context and data model

Semantically zones are the spatio-temporal equivalent of periods and locations. Zones are represented in the data model by the interface Zone and along with it the following interfaces are also established.

  • ZonalIdentifier,

  • ZoneClass, and

  • RSUsingZonalIdentifiers.

Referring to Figure 8, a ZonalIdentifier is either a zonal identifier primitive or a compound of two zonal identifier primitives, one spatial and one temporal.

Figure 8 — Primitives of ZonalIdentifier

Referring to Figure 9, a Zone is either a zonal primitive or a compound of two zonal primitives, one spatial and one temporal.

Figure 9 — Primitives of Zone

Referring to Figure 10, a ZoneClass is either a zonal class primitive or a compound of two zonal class primitives, one spatial and one temporal.

Figure 10 — Primitives of ZoneClass

Referring to Figure 11, an RSUsingZonalIdentifiers is either a zonal RS using identifiers primitive or a compound of two of its primitives, one spatial and one temporal.

Figure 11 — Primitives of RSUsingZonalIdentifiers

Referring to Figure 12, Zone, ZonalIdentifier and ZoneClass come together to form RSUsingZonalIdentifiers.

Figure 12 — Components of RSUsingZonalIdentifiers

7.3.3.2.  Defining tables

  1. Table 28 — Elements of Zonal RS using Identifiers::RSUsingZonalIdentifiers

  2. Table 29 — Elements of Zonal RS using Identifiers::RSUsingZonalIdentifiersCompound

  3. Table 30 — Elements of Zonal RS using Identifiers::RSUsingZonalIdentifiersPrimitive

  4. Table 31 — Elements of Zonal RS using Identifiers::ZonalIdentifier

  5. Table 32 — Elements of Zonal RS using Identifiers::ZonalIdentifierComplex

  6. Table 33 — Elements of Zonal RS using Identifiers::ZonalIdentifierPrimitive

  7. Table 34 — Elements of Zonal RS using Identifiers::Zone

  8. Table 35 — Elements of Zonal RS using Identifiers::ZoneClass

  9. Table 36 — Elements of Zonal RS using Identifiers::ZoneClassComplex

  10. Table 37 — Elements of Zonal RS using Identifiers::ZoneClassPrimitive

  11. Table 38 — Elements of Zonal RS using Identifiers::ZoneCompound

  12. Table 39 — Elements of Zonal RS using Identifiers::ZonePrimitive

Table 28 — Elements of Zonal RS using Identifiers::RSUsingZonalIdentifiers

Name:

RSUsingZonalIdentifiers

Definition:

A reference system using zonal identifiers is either a reference system using zonal identifiers primitive or a compound of one spatial reference system using zonal identifiers and one temporal reference system using period identifiers primitives.

Stereotype:

Interface

Generalization of:

RSUsingZonalIdentifiersCompound, RSUsingZonalIdentifiersPrimitive

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

M

*

comprises

Zone (feature type)

M

*

comprises

Public attributes:

(none)

Constraints:

(none)


Table 29 — Elements of Zonal RS using Identifiers::RSUsingZonalIdentifiersCompound

Name:

RSUsingZonalIdentifiersCompound

Definition:

A reference system using zonal identifiers compound is a compound of one spatial reference system using zonal identifiers and one temporal reference system using zonal identifiers primitives.

Stereotype:

Interface

Inheritance from:

RSUsingZonalIdentifiers

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

RSUsingZonalIdentifiersPrimitive (feature type)

M

2

element

Public attributes:

(none)

Constraints:

(none)


Table 30 — Elements of Zonal RS using Identifiers::RSUsingZonalIdentifiersPrimitive

Name:

RSUsingZonalIdentifiersPrimitive

Definition:

A reference system using zonal identifiers primitive is either a spatial reference system using geographic identifiers or a temporal reference system using period Identifiers.

Stereotype:

Interface

Inheritance from:

RSUsingZonalIdentifiers

Abstract:

true

Associations:

(none)

Public attributes:

(none)

Constraints:

(none)


Table 31 — Elements of Zonal RS using Identifiers::ZonalIdentifier

Name:

ZonalIdentifier

Definition:

Spatial, temporal or spatio-temporal reference in the form of a label or code that identifies a zone.

Stereotype:

DataType

Generalization of:

ZonalIdentifierComplex, ZonalIdentifierPrimitive

Abstract:

true

Associations:

(none)

Public attributes:

(none)

Constraints:

(none)


Table 32 — Elements of Zonal RS using Identifiers::ZonalIdentifierComplex

Name:

ZonalIdentifierComplex

Definition:

Zonal identifier complex is a complex of two zonal identifier primitives, one geographic identifier and one period identifier.

Stereotype:

DataType

Inheritance from:

ZonalIdentifier

Abstract:

true

Associations:

Association with:

Obligation

Maximum occurrence

Provides:

ZonalIdentifierPrimitive (feature type)

M

2

element

Public attributes:

(none)

Constraints:

(none)


Table 33 — Elements of Zonal RS using Identifiers::ZonalIdentifierPrimitive

Name:

ZonalIdentifierPrimitive

Definition:

Zonal identifier primitive is either a geographic identifier or a period identifier.

Stereotype:

DataType

Inheritance from:

ZonalIdentifier

Abstract:

true

Associations:

(none)

Public attributes:

(none)

Constraints:

(none)


Table 34 — Elements of Zonal RS using Identifiers::Zone

Name:

Zone

Definition:

A zone is a particular spatial, temporal or spatio-temporal place.

Stereotype: