@UML(identifier="SC_CompoundCRS", specification=ISO_19111) public interface CompoundCRS extends CoordinateReferenceSystemA coordinate reference system describing the position of points through two or more independent coordinate reference systems. Thus it is indirectly associated with two or more coordinate systems and datums by defining the compound CRS as an ordered set of two or more instances of
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
- Engineering (1D linear) + Vertical
TemporalCRSadded. 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.
All Methods Instance Methods Abstract Methods Modifier and Type Method Description
getComponents()The ordered list of coordinate reference systems.
Methods inherited from interface IdentifiedObject
getAlias, getIdentifiers, getName, getRemarks, toWKT
@UML(identifier="componentReferenceSystem", obligation=MANDATORY, specification=ISO_19111) List<CoordinateReferenceSystem> getComponents()The ordered list of coordinate reference systems.
Departure from OGC/ISO specification:
- the ordered list of coordinate reference systems.
ISO 19111 said "nesting of compound CRSs shall not be permitted; the individual single systems shall be aggregated together". However this approach causes data lost: it is difficult to add a temporal CRS to an existing three-dimensional compound CRS without loosing the name and identifiers of the 3D CRS, unless nesting is permitted. It is programmatically easier to convert nested CRSs to a flat list of single CRSs when needed than to reconstruct the 3D CRS from the single components. Consequently GeoAPI has been keep conformant with the legacy OGC 01-009 specification in this aspect, which were allowing nested compound CRS.