Module org.opengis.geoapi

Package org.opengis.referencing.crs

Interface CompoundCRS

All Superinterfaces:

CoordinateReferenceSystem, IdentifiedObject, ReferenceSystem

@UML(identifier="CompoundCRS",
     specification=ISO_19111)
public interface CompoundCRS
extends CoordinateReferenceSystem

A CRS describing the position of points through two or more independent CRSs. Two CRSs are independent of each other if coordinate values in one cannot be converted or transformed into coordinate values in the other.

For spatial coordinates, a number of constraints exist for the construction of compound CRSs. For example, the CRSs that are combined should not contain any duplicate or redundant axes. Valid combinations include (non-exhaustive list):

• Geographic 2D + Vertical
• Geographic 2D + Engineering 1D (near vertical)
• Projected 2D + Vertical
• Projected 2D + Engineering 1D (near vertical)
• Engineering (horizontal 2D) + Vertical
• Engineering (1D linear) + Vertical

Any coordinate reference system (CRS), or any of the above listed combinations of CRSs, can have a TemporalCRS added. More than one temporal CRS may be added if these axes represent different time quantities.

Since:

1.0

See Also:

• CRSAuthorityFactory.createCompoundCRS(String)
• CRSFactory.createCompoundCRS(Map, CoordinateReferenceSystem[])

Field Summary

Fields inherited from interface org.opengis.referencing.IdentifiedObject

ALIAS_KEY, DOMAINS_KEY, IDENTIFIERS_KEY, NAME_KEY, REMARKS_KEY

Fields inherited from interface org.opengis.referencing.ReferenceSystem

DOMAIN_OF_VALIDITY_KEY, SCOPE_KEY

Method Summary

Modifier and Type	Method	Description
List<CoordinateReferenceSystem>	getComponents()	Returns the ordered list of CRS components.
default CoordinateSystem	getCoordinateSystem()	Returns a view over all coordinate systems of this compound CRS.
default List<SingleCRS>	getSingleComponents()	Returns the ordered list of CRS components, none of which itself compound.

Methods inherited from interface org.opengis.referencing.IdentifiedObject

getAlias, getDomains, getIdentifiers, getName, getRemarks, toWKT

Methods inherited from interface org.opengis.referencing.ReferenceSystem

getDomainOfValidity, getScope

Method Details

getComponents

List<CoordinateReferenceSystem> getComponents()

Returns the ordered list of CRS components. The returned list may contain nested compound CRS. For a list without nesting, as required by ISO 19111, see getSingleComponents().

Why nested compound CRS

The use of nested compound CRSs can avoid metadata lost when a temporal CRS is appended to spatial components defined in a preexisting compound CRS. A three-dimensional compound CRS has its own metadata (e.g., an EPSG code) that may not be found in the individual horizontal and vertical components. A flatten list of horizontal, vertical and temporal components would lost those metadata. In particular, the lost of authority code reduces the scope of the search for coordinate operations that an application can do.

Returns:

the ordered list of components of this compound CRS.

Departure from OGC/ISO standard by generalization

Added as an alternative to the association defined by ISO 19111 for resolving the problem of metadata lost. The ISO 19111 requirement is still available as the #getSingleComponents() method.

getSingleComponents

@UML(identifier="componentReferenceSystem",
     obligation=MANDATORY,
     specification=ISO_19111)
default List<SingleCRS> getSingleComponents()

Returns the ordered list of CRS components, none of which itself compound. If this compound CRS contains nested compound CRS components, then those components are flattened recursively in a sequence of SingleCRS objects.

Returns:

the ordered list of components of this compound CRS, none of which itself compound.

Since:

3.1

getCoordinateSystem

default CoordinateSystem getCoordinateSystem()

Returns a view over all coordinate systems of this compound CRS. The returned coordinate system shall have a dimension equals to the sum of the dimensions of all components, and axes obtained from the coordinate system of each component in the same order.

Specified by:

getCoordinateSystem in interface CoordinateReferenceSystem

Returns:

view over all coordinate systems of this compound CRS.

Departure from OGC/ISO standard by generalization

ISO 19111 defines this method for SingleCRS only. GeoAPI declares this method in CompoundCRS as well for user convenience, because CS dimension and axes are commonly requested information that are still available (indirectly) for compound CRS.