IVOA Web>IvoaSemantics>RFMforUCD>UCDList_1-3_RFM (revision 2)~~EditAttach~~

Request for Modification for the UCD list v1.4 - from May 2017 to Feb 2018

This page is proposed in the new process for UCDs update discussed at the Interop meeting in Shanghai in May 2017. The new Note Maintenance for UCD specification mentions the details of the updating process. When a new UCD term seems necessary to include in the UCD list, a record describing the request for addition can be expressed as followed : new term proposed, rationale, example of usage, etc , as show in the list below.

The term is then discussed within the maintenance committee and the semantics working group and answers from the maintenance committee is given within 1 month.

Every 6 months the list of proposed changes are examined by the TCG and the validated changes are ingested in the new version of Endorsed Note for the UCD1+ list of terms.

Proposals from Solar and Planetary community ( B. Cecconi et al.)

Concept family : electric charge and current

Family : plasma environment
Proposal : phys.flux;phys.charge
Requires : phys.charge with definition : Electric charge and tag : Q
Answer: we understood the need for two concepts : electric current density and electric charge proposal for update:

Status : inserted
Benefits : introduces phys.current; this definition is more focused on the requested concept --> implies better assignment

Concept family: Observation geometry ; Illumination conditions

Case:
- Representation of the various angles : Explained in paper https://doi.org/10.1016/j.pss.2015.06.004
- See figure attached here
- theta_i = Incidence Angle, theta_e = Emergence Angle, alpha = Phase Angle
- The angle phi (azimuth) is not required for illumination condition description (and we already have a UCD for this) from Baptiste Cecconi
Rationale: -from B. Cecconi - 06 July 2017 - see semantics list for the email threads
- In planetary sciences ... our use cases are the following:
- In EPNcore, the illumination conditions are search parameters, we have 6 separate columns for the min/max values of those 3 angles.
- For planetary images or spectra, the product metadata must contain the observation geometry, and those 3 angles are to be there, altogether.

Concept: Incidence angle

Proposal: pos.incidenceAng
Requires:
- definition : Incidence angle
- tag : Q
preliminary answer proposed: pos.posAng.incidence with definition : "Angle of incidence of a vector e.g illumination vector"
Discussion: There is a debate about this (S.Erard): incidence and emergence are physical angles of an optical ray on an interface / can be like pos.phaseAng; then it could logically be hooked under pos directly , as pos.phaseAng
answer: This is understood that we deal here with generic optical angles.

add Q | pos.incidenceAng | Incidence angle of optical ray on an interface

Concept: Emergence angle

proposal: pos.emergenceAng
Requires:
- definition : Emergence angle
- tag : Q
Answer: see discussion about incidence angle

add Q | pos.emergenceAng | Emergence angle of optical ray on an interface

Concept: Azimuth angle

Proposal: pos.azimuthAng
Requires:
- definition : Azimuthal angle
- tag : Q
Discussion: azimuthal angle is already defined in the ucd tree by:
- pos.az.azi exists but implies an alt-azimuthal ccordinate system.
Answer: see discussion about incidence angle

add Q | pos.azimuth | azimuthal angle in a generic reference plane

Concept family: spectroscopic measures

Concept : radiance

Proposal: definition of phot.radiance is not completely adequate. It should be radiant power from the source per unit area (of source) and unit solid angle
Discussion: TBD

Concept : reflectance

Reflectances are relative quantities comparing input radiance or flux to the observed radiance, with various adimensional nomalization, so that their units can't be used for decide which actual physical quantity is shared or plotted. As current spectral analysis tools are using UCDs to decide how to combine data from various sources, there is a need for high level descriptors to sort out the most obvious kinds of normalization of processing. Without this, comparisions between dataset may lead to meaningless results.

proposal: phys.reflectance
rationale: different from albedo, which is valid at a given wavelength or frequency.
definition: This is a radiance factor: observed radiance divided by input radiance. This quantity derives from the surface or interface properties.
annotation master : to check ; consequence : change definition to albedo and remove reflectance
- | phys.albedo | Albedo or reflectance
Discussion: it is preferable to add a new term
Possible derived usage : Radiance Factor : arith.factor;phys.reflectance
Answer: the reflectance term is added.

add Q | phys.reflectance | Radiance factor (received radiance divided by input radiance)

Proposal: phys.reflectance.I_over_F
Rationale: This a specific measured reflectance, which may include the thermal emission of the body. This is defined as the observed radiance, divided by the input illumination flux (solar flux for planetary bodies). No correction for the black body emission is done on this quantity.
Discussion: open

Proposal: phys.reflectance.bidirectional
definition: bidirectional reflectance
- tag : Q
Discussion:The current accepted short name is bidir
Answer: add new term

add Q | phys.reflectance.bidirectional | Bidirectional reflectance

Proposal: phys.brdf
definition: bidirectional reflectance distribution function
- tag: Q
discussion: check if phys.reflectance.bidirectional;instr.det.psf would do ?
- no, this is specific to normalization
Answer: add new term (the current accepted short name is BRDF )

add Q | phys.reflectance.bidirectional.df | Bidirectional reflectance distribution function

Proposal: phys.reflectance.factor
Definition: reflectance normalized per direction cosine of incidence angle ??
- tag : Q
Answer: add new term

add Q | phys.reflectance.factor | Reflectance normalized per direction cosine of incidence angle

NB : check relevance and possible ambiguity with radiance factor...
- for normalized reflectance concept
- proposal arith.ratio;phys.reflectance
- definition : reflectance normalized per reflectance at one wavelength

Concept family: Coordinate frames

Concept : Cylindrical coordinates

proposal: pos.cylindrical
family : SSIG coordinates systems
rationale: no such coordinate branch in the UCD tree yet
definition : Cylindrical coordinates
tag : S

##answer accepted S pos.cylindrical "Related to cylindrical coordinates"

proposal: pos.cylindrical.r
requires :pos.cylindrical
definition : Cylindrical coordinate (radial distance from z-axis)
tag : Q

##answer accepted as pos.cylindrical.r "Radial distance from z-axis (cylindrical coordinates)"

proposal: pos.cylindrical.th
definition : Cylindrical coordinate (Azimuthal angle around z-axis)
tag : Q

##answer The conventions for the name of the angles varies : seehttp://mathworld.wolfram.com/CylindricalCoordinates.html

##answer accepted as pos.cylindrical.azi "Azimuthal angle around z-axis (cylindrical coordinates)"

proposal: pos.cylindrical.z

definition : Cylindrical coordinate (height from reference plane)
tag : Q

##answer accepted as pos.cylindrical.z "Height or altitude from reference plane (cylindrical coordinates)"

## less ambiguous as for angle names

Concept: Spherical Coordinates

proposal: pos.spherical
Rationale: not present in UCD tree definition : spherical coordinates
tag : S

##answer accepted pos.spherical "Related to cylindrical coordinates"

proposal: pos.spherical.r
definition : spherical coordinate (radial distance from origin)
tag : Q

## answer accepted as pos.spherical.r "Radial distance or radius (spherical coordinates)"

proposal: pos.spherical.th
definition : spherical coordinate (colatitude angle)
tag : Q

##answer same as for cylindrical : various angle names depending on definitions ( http://mathworld.wolfram.com/SphericalCoordinates.html )

##answer proposed as pos.spherical.colat "Polar or Colatitude angle (spherical coordinates)"

proposal: pos.spherical.ph
definition : spherical coordinate (Azimuth angle)
tag : Q

##answer proposed as pos.spherical.azi " Azimuthal angle (spherical coordinates)"

Concept : orbital parameters

%Comment perifocal "src.orbital.periastron" exists but is slightly different
%Comment periapsis : check variation in meaning
proposal: src.orbital.periapsis
definition : minimal distance to the center of mass for an orbit
tag : P

##discussion postponed (time to go to lunch)

Concept : rotation params for 3D parameters

##answer

##pos. is the right branch to hook these rotation concepts
_##pos.wcs exist for 2D transformation ; pos.rotation will handle the 3D case --> propose pos.rotation3d_
##theses parameters will be used soon with real data . We decide to delay the addition and will consider several examples

proposal: pos.rotation
definition : Relative to rotation
tag : S
proposal: pos.rotation.eulerAngle
definition : Euler angles vector
tag : V
proposal: pos.rotation.quaternion
definition : rotation quaternion vector
tag : V
proposal: pos.rotation.matrix
definition : rotation matrix
tag : V
proposal: pos.rotation.axis
definition : rotation axis vector
tag : V

Concept: spatial resolution

rationale: linear resolution on cartesian or linear spatial axis as opposed to angular resolution
proposal: pos.resolution
definition : Spatial linear resolution (not angular)
tag : Q

##answer add Q | pos.resolution | Spatial linear resolution (not angular)
##inserted

Concept: heliocentric coordinates

longitude and latitude can be expressed as
proposal: pos.bodyrc.lon;pos.heliocentric
proposal: pos.bodyrc.lat;pos.heliocentric
% induced changes in assign tool: if heliocentric, or centric except geocentric , --> not earth .... change token

##answer agreed to modify assigning tool - done

##discussion: In body-centric coordinates, longitudes are defined from sub-observer point, while body-graphic coordinates are defined from a standard body reference frame

VESPA team to check consistency between heliocentric and planetocentric definitions

##answer add S | pos.bodycentric | Body-centric related coordinate <br/> ##answer add S | pos.bodygraphic | Body-graphic related coordinate

##inserted

Metadata branch

Concept: checksum

proposal: meta.checksum

rationale: to check integrity of data

definition : numerical signature of digital data

tag : Q

##answer add Q | meta.checksum | Numerical signature of digital data <br/>##inserted

Concept: modification date of a dataset

proposal: time.update

definition : modification date for a dataset

##answer : use *time.processing*

done : add update in the definition of this ucd

Other item

Concept: shape of planetary objects

%this is used to represent the 3D shape of object: a 3D lattice

proposal: phys.shape
definition : 3D shape of an object
tag : Q
usage : phys.shape;meta.modelled for a 3D shape model
usage : phys.shape;pos.bodyrc.alt for elevation or terrain model (distribution of altitude on top of a reference ellipsoid or geoid )

##discussion: postponed until a real case is met