org.opengis.referencing.crs
Interface CompoundCRS
- All Superinterfaces:
- CoordinateReferenceSystem, IdentifiedObject, ReferenceSystem
@UML(identifier="SC_CompoundCRS",
specification=ISO_19111)
public interface CompoundCRS
- extends CoordinateReferenceSystem
A coordinate reference system describing the position of points through two or more
independent coordinate reference systems. Thus it is associated with two or more
Coordinate Systems and
Datums by defining the compound CRS
as an ordered set of two or more instances of CoordinateReferenceSystem
.
In general, a Compound CRS may contain any number of axes. The Compound CRS contains an
ordered set of coordinate reference systems and the tuple order of a compound coordinate
set shall follow that order, while the subsets of the tuple, described by each of the
composing coordinate reference systems, follow the tuple order valid for their respective
coordinate reference systems.
For spatial coordinates, a number of constraints exist for the construction of Compound CRSs.
For example, the coordinate reference systems that are combined should not contain any duplicate
or redundant axes. Valid combinations include:
- Geographic 2D + Vertical
- Geographic 2D + Engineering 1D (near vertical)
- Projected + Vertical
- Projected + Engineering 1D (near vertical)
- Engineering (horizontal 2D or 1D linear) + Vertical
Any coordinate reference system, or any of the above listed combinations of coordinate
reference systems, can have a Temporal CRS added. More than one Temporal CRS may be added
if these axes represent different time quantities. For example, the oil industry sometimes
uses "4D seismic", by which is meant seismic data with the vertical axis expressed in
milliseconds (signal travel time). A second time axis indicates how it changes with time
(years), e.g. as a reservoir is gradually exhausted of its recoverable oil or gas).
- Since:
- GeoAPI 1.0
getComponents
@UML(identifier="componentReferenceSystem",
obligation=MANDATORY,
specification=ISO_19111)
List<CoordinateReferenceSystem> getComponents()
- The ordered list of coordinate reference systems.
- Returns:
- The ordered list of coordinate reference systems.
- Since:
- GeoAPI 2.3
Departure from OGC/ISO specification:
According ISO 19111, "A Compound CRS is a coordinate reference system that combines
two or more coordinate reference systems, none of which can itself be compound".
However this constraint greatly increases the cost of extracting metadata (especially the CRS
identifier) of the three-dimensional part of a spatio-temporal CRS. Note also that in
"Coordinate Transformation Services" (OGC document 01-009), a compound CRS was
specified as a pair of arbitrary CRS ("head" and "tail") where each could be another
compound CRS, allowing the creation of a tree. GeoAPI follows that more general strategy.
Copyright © 1994-2011 Open Geospatial Consortium. All Rights Reserved.