PrimeMeridian (GeoAPI normative 3.1-SNAPSHOT)

All Superinterfaces:

IdentifiedObject
```
@UML(identifier="CD_PrimeMeridian",
     specification=ISO_19111)
public interface PrimeMeridian
extends IdentifiedObject
```
A prime meridian defines the origin from which longitude values are determined. Most geodetic datums use Greenwich as their prime meridian.
Constraints:
- If the prime meridian name is “Greenwich” then the value of Greenwich longitude shall be 0 degrees.
- Conversely if the Greenwich longitude value is zero, then the prime meridian name shall be “Greenwich”.
Since:

1.0

See Also:

DatumAuthorityFactory.createPrimeMeridian(String), DatumFactory.createPrimeMeridian(Map, double, Unit)

Field Summary
- Fields inherited from interface IdentifiedObject
  ALIAS_KEY, IDENTIFIERS_KEY, NAME_KEY, REMARKS_KEY

Method Summary

Modifier and Type	Method	Description
`Unit<Angle>`	`getAngularUnit()`	Returns the angular unit of the Greenwich longitude.
`double`	`getGreenwichLongitude()`	Longitude of the prime meridian measured from the Greenwich meridian, positive eastward.

Methods inherited from interface IdentifiedObject
getAlias, getIdentifiers, getName, getRemarks, toWKT

- Method Detail
  - getGreenwichLongitude
```
@UML(identifier="greenwichLongitude",
     obligation=CONDITIONAL,
     specification=ISO_19111)
double getGreenwichLongitude()
```
    Longitude of the prime meridian measured from the Greenwich meridian, positive eastward. The greenwichLongitude default value is zero, and that value shall be used when the meridian name value is "Greenwich".
    
    Returns:
    
    the prime meridian Greenwich longitude, in angular unit.
    
    Unit:
    
    Angle
  - getAngularUnit
```
@UML(identifier="getAngularUnit",
     specification=OGC_01009)
Unit<Angle> getAngularUnit()
```
    Returns the angular unit of the Greenwich longitude.
    
    Returns:
    
    the angular unit of Greenwich longitude.
    
    Departure from OGC/ISO specification:
    This attribute is inherited from an older OGC specification. In ISO 19111, greenwichLongitude is a property of type Angle rather than double, and the unit of measure is part of the Angle value.