Module org.opengis.geoapi

Package org.opengis.referencing.crs

Interface CoordinateReferenceSystem

All Superinterfaces:

IdentifiedObject, ReferenceSystem

All Known Subinterfaces:

CompoundCRS, DerivedCRS, EngineeringCRS, GeneralDerivedCRS, GeocentricCRS, GeodeticCRS, GeographicCRS, ImageCRS, ParametricCRS, ProjectedCRS, SingleCRS, TemporalCRS, VerticalCRS

@Classifier(ABSTRACT)
@UML(identifier="CRS",
     specification=ISO_19111)
public interface CoordinateReferenceSystem
extends ReferenceSystem

Base type of all Coordinate Reference Systems (CRS). This is the base interface for two cases:

• SingleCRS, defined by a coordinate system and a datum or datum ensemble;
• CompoundCRS, defined as a sequence of SingleCRS.

Purpose

A coordinate reference system (CRS) captures the choice of values for the parameters that constitute the degrees of freedom of the coordinate space. The fact that such a choice has to be made, either arbitrarily or by adopting values from survey measurements, leads to the large number of coordinate reference systems in use around the world. It is also the cause of the little understood fact that the latitude and longitude of a point are not unique. Without the full specification of the coordinate reference system, coordinates are ambiguous at best and meaningless at worst.

Spatiotemporal CRS

The concept of coordinates may be expanded from a strictly spatial context to include time. Time is then added as another coordinate to the coordinate tuple. It is even possible to add two time-coordinates, provided the two coordinates describe different independent quantities. An example of the latter is the time/space position of a subsurface point of which the vertical coordinate is expressed as the two-way travel time of a sound signal in milliseconds, as is common in seismic imaging. A second time-coordinate indicates the time of observation.

Since:

1.0

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
CoordinateSystem	getCoordinateSystem()	Returns the coordinate axes with specified units of measure.

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

getCoordinateSystem

CoordinateSystem getCoordinateSystem()

Returns the coordinate axes with specified units of measure. The type of the returned coordinate system should be one of the sub-interfaces defined in the org.opengis.referencing.cs package. The subtype implies the mathematical rules that define how coordinate values are calculated from distances, angles and other geometric elements and vice versa.

An exception to above recommendation is when this CRS is an instance of CompoundCRS. In that case, the coordinate system type may be hidden and the implied mathematical rules are unspecified. However the coordinate system object is still useful as a list of axes.

Returns:

the coordinate axes with specified units of measure.

Departure from OGC/ISO standard by generalization

ISO 19111 defines this method for SingleCRS only. GeoAPI declares this method in this parent interface for user convenience, because CRS dimension and axes are commonly requested information and are always available, directly or indirectly, even for CompoundCRS.