IVOA

Comments on UCDs



You can leave on this page feedback on UCDs.
For example, suggest the creation of new UCDs, or propose to modify or remove existing ones.
The comments on this page can be reviewed and commented by people from the UCD steering comitee, but other contributors are welcome. These contributions will be used to gradually improve the UCD1+.

Please check first the existing list of UCD1+.



The last comments are listed below. Green backgrounds are for suggested new UCDs, orange corresponds to modifications, and red to suppressions.
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UCDDefinitionRemarksSugg. byDateAnswer
time.frameTime frame used for a time measureThis is used in Spectrum DM. Useful for Characterization too.Sebastien Derriere2011/10/17 07:17:33
spect.continuumContinuum spectrum (model or observed)Often people will publish a fit to the continuum component of a spectrum with lines omitted. This UCD is the obvious counterpart to spect.line and I would like to include it in the IVOA Spectrum model.Jonathan McDowell2006/10/22 14:19:55
pos.htmHierarchical Triangular Mesh IndexAFAIK, HTM is defined such that all HTM indices can have the same UCD, but it would be good to check this point with someone who understands the system properly.Guy Rixon2005/03/24 15:02:15
phys.IMFInitial mass function Description of the Initial Mass Function. Note: Althougth it would include something like phy.IMF.mass.max; phy.IMF.mass.min for the mass limits, phy.IMF.powerlaw.slope for a powerlaw IMF, phy.IMF.lognormal.mean for the mean value of a lognormal IMF etc... I think that additional extensions would be difficult, since the IMF would use any functional form, so the UCD would refer to string values (may be it should be used with a "meta" word). Analogously, I suggest to change phy.SFR to phy.SFH (Star Formation History): SFR assumes a functional form or the star fromation (a constant star formation history). SFH is more generalMiguel Cerviño2004/12/27 12:21:40
stat.moment.nthnth moment of a statistical distributionSuch UCD would replace stat.variance and stat.mean by stat.moment.2nd and stat.moment.1st and allows to define additional moments to any statistical distribution like the measure skewness (stat.moment.3rd) or the kurtosis (stat.moment.4th) by the price of add an atom to the word. (Formally, skewness or kurtosis would imply and additional ratio operation with stat.moment.2nd, that I do not know how it can be solved in the current UCD1+. Analogously, it would be a simillar stat.cumulant.nth for cumulants... Miguel Miguel Cerviño2004/12/27 11:02:03
pos.eq.spdsouth polar distance (as declination, but always positive)Andrea2004/10/27 16:25:58
em.IR.10000ADiscussion test with Olga PevunovaPlease, ignore this. Get in touch with Olga Peganova for needsPedro Osuna2004/10/26 01:18:16
object, object.sun, object.planet, object.planet.jupiter, object.planet.saturn, object.satellite, object.satellite.titan, object.asteroid...SOLAR SYSTEM objects based in different types (sun/planet/satellite/asteroid...)For example, the angular separation between Jupiter and Io should be something like this: pos.ang.separation;object.planet.jupiter;object.satellite.io (The idea to put the "object" word in all the UCDs comes when trying to avoid putting something like planet.sun or planet.moon, so that we can put object.sun or object.satellite.moonAleksander Morgado2004/10/23 20:39:09
pos.subsun.lat, pos.subsun.lon, pos.subearth.lat, pos.subearth.lonSub-Earth and Sub-Sun latitude and rotating longitude parameters for planetary measurementsFor example, the Sub-Earth rotating longitude for Saturn (Longitude of the Central Meridian of Saturn in System III) should look like this: pos.subearth.lon;planet.saturnAleksander Morgado2004/10/23 20:27:27
pos.distanceDistance between two objectsReally useful when working with planets and satellites. For example, distance between Earth and Saturn.Aleksander Morgado2004/10/23 20:21:00
Already exists... phys.distance But I really don't know why this UCD is in the PHYS list, and not in the POS list...Aleksander Morgado2004/10/28 17:21:17No
image.x and image.yX-Y standard coordinates of an imageI don't think that the instr.pixel should be used when working with an imageAleksander Morgado2004/10/23 18:56:04
src.netSource minus background valueI would like to distinguish between total flux, background flux and net flux (or counts, or faraday rotation angle, or....) Should we / could we use UCD to do this? If so, we should have src.total, src.net, src.background. These would be "S" secondary words use to qualify some other quantity, most often flux. Jonathan McDowell2004/10/21 06:43:30
meta.versionA field indicating a version (could be a s/w version, a data product version, etc.)The concept of versioning is relevant in various aspects of the VO, from the software to -and here goes my main interest- the version of a product of a given observation. Versions could take the actual form of dates or of running numbers, etc. Hence it could be of the form: meta.version;time or meta.version;meta.numberAlberto Micol2004/10/08 14:22:56
Aleksander Morgado2004/10/23 18:43:27Yes
meta.curationMetadata associated with dataset curationIt would be useful to have UCDs for the various things in the VO Resource Metdata. I would suggest e.g.: meta.human;meta.curation for a contact name for curation. (meta.organization would be useful too.)Jonathan McDowell2004/09/28 14:50:45
stat.amplVariability amplitude (from min to max)I may have missed an existing UCD for this because I would have thought it must be in some Vizier catalogs!Jonathan McDowell2004/09/28 14:47:47
This concept is already described, but it is not under 'stat'! src.var.amplitude="Amplitude of variation" Sebastien Derriere2004/09/28 15:51:29No
phot.flux.beamFlux per resolution element (e.g. Jy/beam)Radio data really needs this, a lot of data is published in it. It's not the same as flux per square arcsecond because the beam may vary in size across an image.Jonathan McDowell2004/09/28 14:45:55
phys.energy-densityRadiation energy density per unit volume (possibly also per unit spectral coordinate interval)Useful for theory data, e.g. extragalactic backgroundsJonathan McDowell2004/09/28 14:44:20
phot.rate (or phot.countrate)Count rate, overall or in a spectral channelphot.count at the moment includes both "count" and "count/s" but these are importantly different, since with "count" you can use counting statistics errors directly for example. I would like to be able to distinguish between count and count/s as we have both phot.flux and phot.fluxDensJonathan McDowell2004/09/28 14:42:45
Of the two I vote phot.countrate (more explicit).Alberto Micol2004/10/08 14:26:10Yes
I answered NO to the proposal, but I agree that the definition of phot.count is incorrect (we should drop "count/s"). An obvious alias for phot.countrate is "arith.rate;phot.count"Andrea2004/10/19 15:38:06No
I accept arith.rate;phot.count as the appropriate UCD! ThanksJonathan McDowell2004/10/21 06:44:54No
em.veloc.radioThe apparent radial velocity using the "radio definition"The FITS spectral WCS document discusses the optical, radio and relativistic "apparent radial velocities" and points out that they are not physical source velocities but rather funny ways of encoding the wavelength. It distinguishes between optical, radio and relativistic definitions of this quantity. I propose em.veloc.radio, em.veloc.optical, em.veloc.beta for these quantities. The "em." shows that they are really spectral coordinates and not true velocities.Jonathan McDowell2004/09/28 14:39:06
stat.error(pos.eq.dec)I would like to be able to associate the uncertainties in one UCD with another UCDHi, I don't know how obvious this is, but the VOTables that I have looked at it hasn't been posible to work out which column an error or uncertainty refers to. I would like a simple method to form these links. Has there been any discusion about this topic? Thanks for any feedback. DavidDavid Rohde2004/09/02 07:58:42
I guess the answer is in VOTable 1.1. The UCD are not meant to bind columns together, but rather to describe every column individually. The UCD for the error on one parameter can be written with the syntax: stat.error;pos.eq.dec (error on declination in that case)

In VOTable 1.1, you can group columns together, to indicate that they are related. This is interesting if you have several declinations with associated errors in the same table. You can build your VOTable like this:
Sebastien Derriere2004/09/02 14:29:49---
src.veloc.orbitThere is already src.orbital.veloc for this concept !Andrea Preite Martinez2004/05/19 18:36:43
meta.crypticThis can be used for very exotic quantities, when no proper UCD existsThis replaces meta.bull***Sebastien Derriere2004/05/19 18:25:22
You can reply to suggesionsSebastien Derriere2004/05/19 18:25:58Yes
?Use this form to send feedback on UCDs...Sebastien Derriere2004/05/18 18:16:48
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