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<h1 style="font-size: 22.75px;">Request for Modification for the UCD list v1.4 - from May 2017 to Feb 2018
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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.)

<span style="color: darkgreen;">#concept : electric current density <br /></span>family: plasma environment <br />proposal: <strong>phys.flux ; phys.charge </strong><br />requires : phys.charge with definition : Electric charge and tag : Q

<em>##answer we understood the need for two concepts : electric current density and electric charge</em> <em>proposal for update:</em>

_add Q | <strong>phys.electCharge</strong> | Electric charge <br />add Q | <strong>phys.current</strong> | Electric current<br />add Q | <strong>phys.current.density</strong> | Electric current density_

_inserted_

_benefits : introduces phys.current; this definition is more focused on the requested concept --&gt; implies better assignment_

<span style="color: darkgreen;">#concept family: Observation geometry ; Illumination conditions</span>

<span style="background-color: transparent;">Representation of the various angles : Explained in paper https://doi.org/10.1016/j.pss.2015.06.004</span>

See figure attached [[http://wiki.ivoa.net/internal/IVOA/RFMforUCD/emergence_incidenceAngle.jpg][here]] <br />theta_i = Incidence Angle, theta_e = Emergence Angle, alpha = Phase Angle <br />The angle phi (azimuth) is not required for illumination condition description (and we already have a UCD for this) <em>from Baptiste Cecconi</em>

#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.

<span style="color: darkgreen;">#concept: Incidence angle<br /></span>proposal: <strong>pos.incidenceAng</strong> <br />requires : <br />definition : Incidence angle<br />tag : Q

_##answer proposed : <strong>pos.posAng.incidence</strong> with definition : "Angle of incidence of a vector e.g illumination vector"_

<em>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;</em> <em>then it could logically be hooked under pos directly , as pos.phaseAng</em>

<em>##agreed:</em> <strong>Q</strong> <strong>pos.incidenceAng</strong> : incidence angle of optical ray on an interface

<span style="color: darkgreen;">#concept: Emergence angle<br /></span>proposal:<strong> pos.emergenceAng</strong><br />definition : Emergence angle<br />tag : Q

<em>##agreed:</em> <strong>Q</strong> <strong>pos.emergenceAng</strong> : emergence angle of optical ray on an interface

_(see discussion for incidence angle)_

<span style="color: darkgreen;"> </span>

<span style="color: darkgreen;">#concept:Azimuth angle</span>

<span style="background-color: transparent; color: #000000;">proposal: </span><strong>pos.azimuthAng</strong>

definition : Azimuthal angle<br />tag : Q

_#answer : azimuthal angle is already defined in the ucd tree by :_

_pos.az.azi exists but implies an alt-azimuthal ccordinate system._

## agreed <strong>Q</strong> <strong>pos.azimuth</strong> : azimuthal angle in a generic reference plane

<span style="color: darkgreen;">#concept: Cylindrical coordinates</span>

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

_##answer accepted <strong>S</strong> <strong>pos.cylindrical</strong> "Related to cylindrical coordinates"_

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

<em>##answer accepted as <strong>pos.cylindrical.r</strong> "R</em><em>adial distance from z-axis </em><em>(cylindrical coordinates)"</em>

proposal: <strong>pos.cylindrical.th </strong><br />definition : Cylindrical coordinate (Azimuthal angle around z-axis)<br />tag : Q

<em>##answer The conventions for the name of the angles varies : see</em><em>http://mathworld.wolfram.com/CylindricalCoordinates.html</em>

<em>##answer accepted as <strong>pos.cylindrical.azi</strong> "</em><em>Azimuthal angle around z-axis (cylindrical coordinates)"</em>

proposal: <strong>pos.cylindrical.z</strong>

definition : Cylindrical coordinate (height from reference plane)<br />tag : Q

<em>##answer accepted as <strong>pos.cylindrical.z</strong> "Height or altitude from reference plane</em> <em>(cylindrical coordinates)"</em>

_## less ambiguous as for angle names_

<span style="color: darkgreen;"> </span>

<span style="color: darkgreen;">#concept Spherical Coordinates</span>

proposal: <strong>pos.spherical</strong><br />Rationale: not present in UCD tree definition : spherical coordinates <br />tag : S

_##answer accepted <strong>pos.spherical</strong> "Related to cylindrical coordinates"_

proposal:<strong> pos.spherical.r </strong><br />definition : spherical coordinate (radial distance from origin)<br />tag : Q

_## answer accepted as <strong>pos.spherical.r</strong> "Radial distance or radius (spherical coordinates)"_

proposal: <strong>pos.spherical.th</strong> <br />definition : spherical coordinate (colatitude angle)<br />tag : Q

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

_##answer proposed as <strong>pos.spherical.colat</strong> "Polar or Colatitude angle (spherical coordinates)"_

proposal: <strong>pos.spherical.ph</strong> <br />definition : spherical coordinate (Azimuth angle)<br />tag : Q

<em>##answer proposed as <strong>pos.spherical.azi</strong> " </em><em>Azimuthal angle (spherical coordinates)</em><em>"</em>

<span style="color: darkgreen;">#concept : orbital parameters <br /></span>%Comment perifocal "src.orbital.periastron" exists but is slightly different<br />%Comment periapsis : check variation in meaning <br />proposal: <strong>src.orbital.periapsis</strong> <br />definition : minimal distance to the center of mass for an orbit<br />tag : P

_##discussion postponed (time to go to lunch)_

<span style="color: darkgreen;"> </span>

<span style="color: darkgreen;">#concept : rotation params for 3D parameters</span>

<span style="color: darkgreen;"> _##answer_ </span>

<em style="background-color: transparent; color: #000000;">##pos. is the right branch to hook these rotation concepts</em><br />_##pos.wcs exist for 2D transformation ; pos.rotation will handle the 3D case --&gt; propose pos.rotation3d_ <br /><em>##theses parameters will be used soon with real data . We decide to delay the addition and will consider several examples</em>

<br />proposal: <strong>pos.rotation</strong> <br />definition : Relative to rotation <br />tag : S<br />proposal: <strong>pos.rotation.eulerAngle </strong><br />definition : Euler angles vector <br />tag : V<br />proposal: <strong>pos.rotation.quaternion </strong><br />definition : rotation quaternion vector<br />tag : V<br />proposal:<strong> pos.rotation.matrix</strong> <br />definition : rotation matrix<br />tag : V<br />proposal: <strong>pos.rotation.axis </strong><br />definition : rotation axis vector<br />tag : V

<span style="color: darkgreen;">#concept: spatial resolution</span>

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

<em>##answer add Q | <strong>pos.resolution</strong> | Spatial linear resolution (not angular)</em> <br /><em>##inserted</em>

<span style="color: #006400;"> </span><span style="color: darkgreen;"><span style="color: #006400;">#concept:</span>heliocentric coordinates <br /></span>longitude and latitude can be expressed as <br />proposal: pos.bodyrc.lon;pos.heliocentric <br />proposal: pos.bodyrc.lat;pos.heliocentric <br />% induced changes in assign tool: if heliocentric, or centric except geocentric , --&gt; not earth .... change token<strong> <br /></strong><br /><em>##answer agreed to modify assigning tool - done</em>

_##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

<em>##answer add S | <strong>pos.bodycentric</strong> | Body-centric related coordinate </em>&lt;br/&gt; <em style="background-color: transparent;">##answer add S | <strong>pos.bodygraphic</strong> | Body-graphic related coordinate</em>

_##inserted_

<strong>%metadata branch<br /></strong><span style="color: #006400;"> </span>

<span style="color: #006400;">#concept: checksum </span><strong><br />proposal: meta.checksum</strong> <br />rationale: to check integrity of data <br />definition : numerical signature of digital data <br />tag : Q

<em>##answer</em> <em>add Q | <strong>meta.checksum</strong> | Numerical signature of digital data </em><em>&lt;br/&gt;</em><em style="background-color: transparent;">##inserted</em>

proposal: <strong>time.update</strong> <br />definition : modification date for a dataset<br /><em>##answer : use <strong>time.processing</strong> <br />done : add update in the definition of this ucd</em> <br /><br /># spectroscopic measures

<span style="color: darkgreen;">#concept : radiance <br /></span>ask for modification of the definition in the UCD list : should be radiant power from the source per unit area (of source) and unit solid angle

<span style="color: darkgreen;">#concept : reflectance <span style="background-color: transparent;"> </span></span>

proposal: <strong>phys.reflectance</strong> <br />rationale : different from albedo <br />definition: the radiance divided by solar flux : I over F

usage : radiance factor, (received radiance divided by input radiance) , may include thermal emission <br />% annotation master : to check ; consequence : change definition to albedo and remove reflectance <br />% | phys.albedo | Albedo or reflectance<br />derived usage : Radiance Factor : arith.factor;phys.reflectance<br /><br /><em>##answer add Q | phys.reflectance | Radiance factor, (received radiance divided by input radiance), may include thermal emission</em>

proposal: <strong>phys.reflectance.bidirectional</strong> <br />definition : bidirectional reflectance <br />tag : Q

_##answer add Q | <strong>phys.reflectance.bidirectiona</strong>l | Bidirectional reflectance_

proposal: <strong>phys.brdf</strong> <br />rationale : specific term as much as psf for the community <br />definition : bidirectional reflectance distribution function <br />tag: Q

_##discussion: check if phys.reflectance.bidirectional;instr.det.psf would do ?_

_##answer add Q | phys.reflectance.bidirectional.df | Bidirectional reflectance distribution function_

proposal: <strong>phys.reflectance.factor </strong><br />definition : reflectance normalized per direction cosine of incidence angle ??<br />tag : Q

_##answer add Q | phys.reflectance.factor | Reflectance normalized per direction cosine of incidence angle_

<em>nb : check relevance and possible ambiguity with radiance factor... <br /></em>

%for normalized reflectance concept<br />proposal <strong>arith.ratio;phys.reflectance</strong> <br />definition : reflectance normalized per reflectance at one wavelength <br /><br />#shape of planetary objects<br />%this is used to represent the 3D shape of object: a 3D lattice<br /><br />proposal: <strong>phys.shape</strong><br />definition : 3D shape of an object <br />tag : Q<br />usage : phys.shape;meta.modelled for a 3D shape model<br />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_

# spectral polarization data <br />#concept :spatial matrix<br />rationale: helps to identify or characterize measurement type

<br />proposal: <strong>phys.polarization.coherenceMatrix</strong><br />definition: coherence matrix of radio signals <br />usage phys.polarisation.coherenceMatrix:instr<br />tag:Q

<em>##answer</em> <em>add Q |<strong> phys.polarization.coherency</strong> | Matrix of the correlation between components of an electromagnetic wave</em>

_This will work for all electromagnetic signals and not only in radio regime_

_not compatible to instr branch in the UCD tree._
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* Set ALLOWTOPICRENAME = IVOA.TWikiAdminGroup<br />--&gt;

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Topic revision: r1 - 2018-03-05 - MireilleLouys
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