This object defines a domain space. i.e.: it describes the set of possible coordinate values.
coords:CoordSpace
The abstract parent class for all coordinate axis types. We provide concrete classes for the most common types of data, Continuous, Binned, and Discrete, but allow extension for other types as needed.
coords:Axis
Freeform string, provides the name or label for the axis.
coords:Axis.name
Axis description for continuous data. This object describes the domain for a particular axis of the domain space. It allows for the specification of the legal domain range (min,max), and a flag indicating if the axis is cyclic.
coords:ContinuousAxis
Minimum extent of the axis domain space. If not provided, the domain space is considered to have no lower bound (-INFINITY).
coords:ContinuousAxis.domainMin
Maximum extent of the axis domain space. If not provided, the domain space is considered to have no upper bound (+INFINITY).
coords:ContinuousAxis.domainMax
Flag indicating if the axis is cyclic in nature. If not provided, it is assumed to be FALSE.
coords:ContinuousAxis.cyclic
Axis description for binned data, where values along the axis correspond to a bin number.
coords:BinnedAxis
The length, or number of bins, along the axis.
coords:BinnedAxis.length
Axis type specifically intended for enumerated coordinates. Since the content and nature of this axis type is heavily dependent on the use case, we define no additional metadata here. Extensions of this type may include additional metadata relevant to the particular use cases. For example, an extension could include the allowed set of values.
coords:DiscreteSetAxis
This is the abstract, empty, base class for all coordinate frames. Coordinate frames provide metadata associated with the coordinate domain space. Typically, this will be related to the origin and orientation of the axes, but might include any metadata which pertains to the definition of the domain.
coords:CoordFrame
The generic coordinate frame is for cases where a domain-specific frame (e.g.: Space, Time), is not required, but the relevant reference metadata is still needed (e.g.: for Redshift or Spectral data)
coords:GenericFrame
Spatial location in phase space (position and velocity) at which the observed value is considered to have been taken. This will typically be given by a standard reference position, but we allow for custom locations as well.
coords:GenericFrame.refPosition
A planetary ephemeris MAY be provided, and SHOULD be provided whenever appropriate, to indicate which solar system ephemeris was used. If needed, but not provided, it is assumed to be "DE405"
coords:GenericFrame.planetaryEphem
A SpaceFrame is specified by its reference frame (orientation), and a reference position (origin). Currently only standard reference frames are allowed. An equinox MUST be provided for pre-ICRS reference frames. A planetary ephemeris MAY be provided if relevant. If needed, but not provided, it is assumed to be "DE405".
coords:SpaceFrame
The spatial location at which the coordinates are considered to have been determined. This model supports locations provided as either a standard reference position (e.g. GEOCENTER), or a coordinate specifying a custom location (e.g. long, lat, height ).
coords:SpaceFrame.refPosition
The spatial reference frame. Values MUST be selected from the controlled vocabulary at the given URL.
coords:SpaceFrame.spaceRefFrame
Reference date for the frame, required for pre-ICRS reference frames.
coords:SpaceFrame.equinox
Ephemeris file for solar system objects SHOULD be specified whenever relevant.
coords:SpaceFrame.planetaryEphem
A TimeFrame SHALL include a time scale and reference position. It MAY also include a reference direction.
coords:TimeFrame
The spatial location at which the coordinate is considered to have been taken. This model supports locations provided as either a standard reference position (e.g. GEOCENTER), or a coordinate specifying a custom location (e.g. long, lat, height).
coords:TimeFrame.refPosition
The time scale sets the reference frame. The value MUST be selected from the controlled vocabulary at the given URL.
coords:TimeFrame.timescale
The reference direction is needed if the time stamps are transformed to a time frame with a different reference position. In those situations, the solar system ephemeris also comes into play. See: FITS WCS Paper IV for details, but in short: The reference direction, presumably the direction to the thing being observed, is used in conjunction with the reference position and planetary ephemeris to determine the correction applied for the path length change. To be fully useful, one also needs to know the location at which the observation was made ( i.e. the observatory location), which is not considered to be Frame metadata.
coords:TimeFrame.refDirection
The AstroCoordSystem object holds a collection of component coordinate system descriptions across all represented physical domains.
coords:AstroCoordSystem
The PixelCoordSystem provides a complete description of the pixel coordinate space. It SHALL contain one PixelSpace instance describing each pixel axis.
coords:PixelCoordSystem
A PixelSpace SHALL include one or more BinnedAxis objects describing the pixel coordinate space. A handedness value MAY be provided to specify the relative orientation of the axes.
coords:PixelSpace
Specifies the handedness of the coordinate space.
coords:PixelSpace.handedness
Abstract head of the coordinate system object tree.
coords:CoordSys
Coordinate system description for any physical domain, such as Time, Space, Redshift, Temperature, Flux, etc.
coords:PhysicalCoordSys
Specialized coordinate system for generic, one-dimensional domains not covered by other, more concrete objects. If a CoordSpace is not provided, it is assumed to be represented by a Standard 1-Dimensional Coordinate Space as described in Appendix B.
coords:GenericSys
Specialized coordinate system for the Spatial domain. This object SHOULD include an appropriate SpaceFrame. In Appendix B, we define two standard spatial coordinate space instances (Spherical and Cartesian), which may be referenced in serializations. If a CoordSpace is not provided, it is assumed to be represented by a Standard Spherical Coordinate Space.
coords:SpaceSys
Specialized coordinate system for the Temporal domain. This object SHOULD include an appropriate TimeFrame. If a CoordSpace is not provided, it is assumed to be represented by a Standard 1-Dimensional Coordinate Space as described in Appendix B.
coords:TimeSys
Abstract head of coordinate spaces related to physical properties.
coords:PhysicalCoordSpace
Generic, one-dimensional coordinate space suitable for use with most non-spatial properties. In Appendix B, we provide the description of a Standard 1D Coordinate Space instance which may be referenced in serializations.
coords:GenericCoordSpace
Spatial domain, three-dimensional spherical coordinate space. The particulars of the axis descriptions depend on the flavor of space being instantiated. In Appendix B., we provide a Standard Spherical Coordinate Space instance which applies to many Astronomical use cases. It provides the default space for SpaceSys instances, and may be referenced in serializations.
coords:SphericalCoordSpace
Spatial domain, three-dimensional cartesian coordinate space. The particulars of the axis descriptions depend on the physical constraints of the instance. In Appendix B, we provide the description of a Standard Cartesian Coordinate Space instance which applies to many Astronomical cases, and may be referenced in serializations.
coords:CartesianCoordSpace
Abstract base class for the Coordinate data types which represent an absolute location within a coordinate space. Coordinates MUST refer to a coordinate system, providing additional metadata relevant to interpreting the coordinate value, and its representation.
coords:Coordinate
Provided additional metadata relevant to interpreting the coordinate value; for example, the spatial reference position, or time scale, axis descriptions.
coords:Coordinate.coordSys
Coordinate value type specifically intended for binned data (e.g.: pixel indexes).
coords:BinnedCoordinate
The binned coordinate value, expressed as an integer. e.g.: bin number, pixel index.
coords:BinnedCoordinate.cval
Specialized BinnedCoordinate for the pixel domain for a 1-dimensional pixel index. PixelIndex MUST refer to a PixelCoordSystem.
coords:PixelIndex
The most common type of coordinate value. This type is appropriate for any data whose values can be described by an ivoa:Quantity (numeric, with unit).
coords:PhysicalCoordinate
This coordinate MUST contain a value expressed as an ivoa:Quantity.
coords:PhysicalCoordinate.cval
Multi-dimensional spatial coordinate. The Point MUST refer to a spatial coordinate system (SpaceSys). The coordinate values map, in order, to the axes described by the associated CoordSpace. Values for unused/undefined dimensions need not be provided.
coords:Point
Coordinate value along the first axis of the associated coordinate space, expressed as an ivoa:Quantity.
coords:Point.axis1
Coordinate value along the second axis of the associated coordinate space, expressed as an ivoa:Quantity.
coords:Point.axis2
Coordinate value along the third axis of the associated coordinate space, expressed as an ivoa:Quantity.
coords:Point.axis3
This is the abstract basis for a set of simple time domain coordinates which are expected to accommodate the vast majority of use cases. All TimeStamps, by definition, exist in a standard 1-D coordinate space, with domainMin|Max of +/-Infinity. All TimeStamps MUST refer to an appropriate TimeSys.
coords:TimeStamp
Time is given as an offset from a specific point in time (time0).
coords:TimeOffset
The TimeOffset coordinate value.
coords:TimeOffset.time
The reference time from which the offset is calculated. This MUST be given as a TimeInstant (e.g.: JD, MJD, ISOTime).
coords:TimeOffset.time0
TimeStamps which specify a specific instant in time. We define three subtypes (ISOTime, JD, MJD), which allow users to explicitly identify the representation and interpretation of the TimeInstant.
coords:TimeInstant
Extension of TimeInstant for time expressed in Julian days. Note that JD does not properly specify a time stamp unless it is related to a time scale and reference position. Precision can easily become an issue with JD, as the numbers tend to be large.
coords:JD
The JD coordinate value. JD dates are dimensionless, with implied units in days.
coords:JD.date
Extension of TimeInstant for time expressed in Modified Julian Days. T(MJD) = T(JD) - 2400000.5.
coords:MJD
The MJD coordinate value. MJD dates are dimensionless, with implied units in days.
coords:MJD.date
Extension of TimeInstant for time expressed as a structured datetime string.
The string representation of a datetime value should follow the FITS convention for representing dates (Hanish and Farris et al, 2001). The FITS standard is effectively ISO8601 format without the 'Z' tag to indicate UTC: YYYY-MM-DD['T'hh:mm:ss[.SSS]]. The TimeScale is provided in the associated TimeFrame.
coords:ISOTime
The ISOTime coordinate value.
coords:ISOTime.date
Abstract head of the polarization coordinate types. Current use cases only require support for discrete polarization states, however, we include this head class to facilitate extension for other types (eg: polarization fraction and angle).
coords:PolCoordinate
Coordinate type for discrete polarization states.
coords:PolState
The coordinate value MUST be from the PolStateEnum enumerated set.
coords:PolState.cval
RefLocation defines the origin of the spatial coordinate space. This location is represented either by a standard reference position (for which the absolute location in phase space is known by definition), or a specified point in another Spatial frame. This object is used as the origin of the SpaceFrame here, but also to specify the Spatial Reference Position (refPosition) associated with other domain Frames. For example, in the Time domain, the Spatial Reference Position indicates that the 'time' values are the time that the 'event' occured at that location, which might be different from the detector location.
coords:RefLocation
An absolute a-priori known location in phase space (position and velocity). Values are selected from the StdRefPosition vocabulary. Considering that the GEOCENTER is really the only place for which we know the absolute location at all times, all other locations require the specification of a planetary ephemeris. LSR[KD] are reserved for spectral and reshift frames. TOPOCENTER (location of the observer) is special in that it assumes that the observing location is available through other means (e.g. a geographic location or an orbit ephemeris). RELOCATABLE is available for simulations. UNKNOWN should only be used if absolutely necessary.
coords:StdRefLocation
Standard reference location. Values MUST be selected from the controlled vocabulary at the given URL.
coords:StdRefLocation.position
A custom reference location in phase space (position and velocity). Position and velocity are given as coordinates with an associated SpaceFrame. An epoch MAY be provided to further refine the location.
coords:CustomRefLocation
Epoch for the reference location.
coords:CustomRefLocation.epoch
The spatial coordinates of the reference location.
coords:CustomRefLocation.position
The velocity of the reference location.
coords:CustomRefLocation.velocity
We define epoch as a primitive data type with the expected form "<type><year>" where type = "J" or "B" for Julian or Besselian respectively, and year is expressed as a decimal year. e.g.: "B1950", "J2000.0"
coords:Epoch
The handedness of a coordinate space. For most cases, this will be a fixed value in the specification of the coordinate space. We provide this element to allow this flexibility when needed. In this document, it is used in the Pixel domain.
coords:Handedness
positive x and y axes point right and up, the positive z axis points inward
coords:Handedness.left
positive x and y axes point right and up, the positive z axis points outward
coords:Handedness.right
Polarization states: Stokes, Circular, Linear and Vector states
coords:PolStateEnum
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.I
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.Q
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.U
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.V
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.RR
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.LL
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.RL
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.LR
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.XX
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.YY
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.XY
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.YX
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.PF
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.PP
TODO : Missing description : please, update your UML model asap.
coords:PolStateEnum.PA