Wikidata:Property proposal/Martian coordinates

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Martian coordinates[edit]

Originally proposed at Wikidata:Property proposal/Natural science

   Done: no label (P10628) (Talk and documentation)
Descriptionplanetocentric coordinates of a place on Mars with longitudes from 0° to 360° (East)
Representsplanetocentric Martian coordinates (Q106948918)
Data typeGeographic coordinates
Domainlocation on Mars (Q111)
Allowed valueslongitude: 0 to 360, latitude: -90 to 90
Example 1Ptolemaeus (Q2886300) → 45°52'48"S, 202°24'0"E
Example 2Olympus Mons (Q520) → 18°39'0"N, 226°12'0"E
Example 3Bradbury Landing (Q4954422) → 4°35'22.2"S, 137°26'30.1"E
Planned use~2000 coordinates currently in P625
See also


Motivation[edit]

lunar coordinates (BEING REPLACED) (P8981) was created per the discussion at Wikidata:Property proposal/lunar coordinates. It's implementation seems to have gone fairly smoothly and addressed the problems identified with P625 used before.

Problems identified when P625 is used
In the earlier discussion at Wikidata:Property proposal/planetary coordinates, we had identified a series of problems with using coordinate location (P625) for places on Mars (or other non-Earth bodies):
  • Method varies from one astronomical body (planet/satellite/asteroid/) to another
  • Wikimedia functions for maps don't all correctly check for globe and generally need custom code to "exclude" non-Earth locations.
  • Users might incorrectly assume that P625 is the only property for coordinates. However, we already have a series of separate properties for places on Earth and a group of properties for celestial coordinates
  • Wikidata Query Server has some handling of globes, notably functions have a globe parameter. However, the globe needs to be hard-coded and distance adjusted for the globe. Accordingly, queries need to be globe specific

Also:

  • Interface doesn't support setting globes
  • Current application at Commons has a problem with the inclusion of places on the Moon in coordinate location (P625)
  • Applications working with both Earth and moon coordinates on WMF sites seem rare (or inexistent)

This is a proposal for a similar property for Mars. We have ca. 2000 places with coordinates.

For Mars, two coordinate systems might be considered:

  • a planetocentric system with longitude East: 0-360, i.e. all positive or zero
  • a planetographic system with longitude West: 0-360, i.e. all negative or zero

P625 currently uses mostly planetocentric coordinates (i.e. positive longitude values). Accordingly, I'd do the same for this.

@ArthurPSmith, Paperoastro: can you help me complete/double-check the proposal? Should we do a second proposal for planetographic coordinates (Add your motivation for this property here.) --- Jura 09:13, 28 May 2021 (UTC)[reply]

Discussion[edit]

  •  Support Proposal looks good to me. I added a couple more examples. Planetocentric seems to be mostly what's used now with P625, or can we tell? ArthurPSmith (talk) 17:29, 28 May 2021 (UTC)[reply]
    • Thanks. When I checked, all but ca. 10 had longitude ≥ 0. Maybe one bot uploaded most of them. Obviously, we could still create a second property for planetographic coordinates. --- Jura 11:46, 29 May 2021 (UTC)[reply]
  •  Support This proposal goes in the right direction. Is it possible to use a qualifier to distinguish planetocentric and planetographic, instead of two different properties? --Paperoastro (talk) 13:38, 30 May 2021 (UTC)[reply]
  •  Support, an important property for science.--Arbnos (talk) 13:25, 31 May 2021 (UTC)[reply]
  •  Oppose The idea of having a distinct property for each coordinate system goes into the wrong direction, as I have already noted in the "planetary coordinates" discussion. The underlying datatype of coordinate location (P625) supports arbitrary coordinates, referenced by an IRI. We should rather strive to get a user interface for selecting the coordinate system. Toni 001 (talk) 07:46, 1 June 2021 (UTC)[reply]
  •  Oppose Per Toni 001's comments. Do we really want a separate property for every planet? This will be unsustainable in the long term and it would be simpler to just use coordinate location (P625) in all applicable places. — The Erinaceous One 🦔 04:24, 18 June 2021 (UTC)[reply]
    • What leads you to conclude that? The problem with the "one fits all" approach was previously discussed and the section "Problems identified when P625 is used" details them. --- Jura 12:12, 20 June 2021 (UTC)[reply]
  • @Toni 001, The-erinaceous-one: While this was already discussed in some depth previously (see links), I do want to re-emphasize a few points here:
      1. The vast majority of coordinate location (P625) entries now and for the foreseeable future refer to Earth. Using the same property to refer to coordinates on other planets is confusing even if the UI is fixed to handle this (and I've seen no sign of any plans to work on this); most third-party users will simply assume it refers to an Earth location and not even bother to check since that is a correct assumption in 99+% of cases.
      2. Most known planets do not currently and likely will never have defined coordinate systems. Jupiter, Saturn, Uranus and Neptune don't have a visible fixed surface. Most planets detected so far around other stars are also gas giants with the same issue; even for the rocky planets around other stars it will likely be decades or more before we have the ability to detect any surface features that could define a coordinate system.
      3. Moons and asteroids within the solar system will probably be the largest class for which coordinate systems could be defined in this century; by the time we have a large number of surface features known on those smaller bodies I would hope the Wikidata UI can have been fixed to handle the globe issue, and third-party uses would hopefully understand that an "asteroid coordinates" property needs to check on which body it refers to.
  • so in the meantime I think this and the one or two other proposals along these lines that we could use (Venus and Mercury probably) are clearly useful. ArthurPSmith (talk) 14:36, 21 June 2021 (UTC)[reply]
* Regarding third-party users in point 1: Isn't that similar to quantities where you check which unit is being used? In the case of coordinates, you check which system is used.
* There are a couple of coordinate systems for planets explained here: https://vgrmag.gsfc.nasa.gov/planetary.html .
Toni 001 (talk) 08:05, 22 June 2021 (UTC)[reply]
@Toni 001: Quantities do not have the same exact unit that applies to 99+% of usage. Yes ideally users/applications would check this, but it's unlikely to be a development priority and if that's not done it will (does already - see Commons) lead to errors. On the coordinate systems for Jupiter, Saturn, etc. - yes they can be defined, but they are used for locating the position of an object in space near Jupiter (and no such object would be permanently fixed), not for locating fixed surface features. If we have Wikidata events located in both space and time in the Jupiter region then perhaps such a coordinate system might be used. Comet Shoemaker–Levy 9 (Q3076) for example ended its life at a particular point in a Jupiter coordinate system (or a set of such points as it broke up) - however I don't see any Jupiter coordinates applied to that Wikidata item right now, and it's unlikely to be something that would have great value. Great Red Spot (Q194256) for example has no fixed location in Jupiter coordinates, nor does anything else we have or would have an item for that I can imagine. ArthurPSmith (talk) 19:38, 22 June 2021 (UTC)[reply]
@ArthurPSmith, Jura1: You have convinced me that there isn't good reason to use coordinate location (P625) for extraterrestrial coordinates, but I don't think that creating a separate property for planets and moons individually is the right approach since there are simply too many. For example, Saturn and Juptiter have several dozen moons between them, and at least some of them have features with coordinate location (P625) statements, such as Sotra Patera (Q128514) on Titan. What if we instead made a single alternative to P625 with a label along the lines of "extraterrestrial coordinate location"? Then we can add a required qualifier for "coordinate system" to specify where the coordinates refer to. For Q128514, this would make the statement Sotra Patera (Q128514)"extraterrestrial coordinate location"12°30'S, 39°48'E"coordinate system""Titan coordinates". — The Erinaceous One 🦔 05:52, 23 June 2021 (UTC)[reply]
@The-erinaceous-one: That was essentially the previous proposal at Wikidata:Property proposal/planetary coordinates, though without the additional qualifier (the existing "globe" component of coordinate location values works for this, but maybe a qualifier would be helpful too?). But we certainly need some sort of catch-all here - User:Jura1 do you want to try that now? ArthurPSmith (talk) 13:27, 23 June 2021 (UTC)[reply]
That was the initial proposal (that was in the air for some time and I formulated at the linked page), but an approach per planet was preferred. Maybe we can revisit the question once made this property and properties for a few others. --- Jura 10:51, 27 June 2021 (UTC)[reply]
@The-erinaceous-one: shall we proceed with this one? --- Jura 11:05, 6 July 2021 (UTC)[reply]
@Jura1: I'm not sure I follow your comment. Are you suggesting that we wait till we have made the proposed property, and several others, before we decide whether to have universal "non-Earth coordinate" property? If so, I disagree. We know that there are a lot of extraterrestrial bodies that will need coordinate locations, so I think it would be shortsided not to simply plan for them now. — The Erinaceous One 🦔 07:18, 7 July 2021 (UTC)[reply]
@The-erinaceous-one: no, the question is if we should be create the "catch-all" property, that @ArthurPSmith: mentioned, for whatever remains once we created the whatever we currently need. As Arthur noted, there not "lot of extraterrestrial bodies that will need coordinate locations", or at least currently there are only a few. We should try to structure content that exists and, as enumerated above, the P625 has too many issues. --- Jura 09:18, 11 July 2021 (UTC)[reply]
If we go the route of splitting the property, could we agree that this should be considered temporary, even if "temporary" means potentially years? We have a nice representation of coordinate system-tagged coordinates in RDF and JSON, and our ultimate goal should be to make use of it. Using a) separate properties for each system or b) one other property with qualifiers make the representation more complicated.
I'm not convinced by the argument that it's too hard for developers to take into account the coordinate system. There is very nice documentation:
https://www.mediawiki.org/wiki/Wikibase/Indexing/RDF_Dump_Format
https://doc.wikimedia.org/Wikibase/master/php/md_docs_topics_json.html
Checking whether the value for "globe" is "Q2" seems relatively easy. Toni 001 (talk) 11:04, 24 June 2021 (UTC)[reply]
Maybe if technology evolves, but to check 9000 values to find 2 isn't really straightforward. BTW, the coordinate systems isn't "nice"ly represented "in RDF and JSON". You are mixing this with the globe parameter (that indicates the planet). --- Jura 10:51, 27 June 2021 (UTC)[reply]
@Toni 001: Which property are you referring to when you say "splitting the property"? Do you mean coordinate location (P625)? — The Erinaceous One 🦔 07:18, 7 July 2021 (UTC)[reply]
Correct. Toni 001 (talk) 09:05, 7 July 2021 (UTC)[reply]

@Toni 001, The-erinaceous-one: I'm sorry to ping you, but you are the unique users that opposed to the creation of this property. Please, explain me, at now, how to distinguish in a query a place on Earth or on Mars, or on Moon. --Paperoastro (talk) 08:06, 21 December 2021 (UTC)[reply]

Dear @Paperoastro: The idea is to navigate from the item to the value node (see this diagram), which has available all the properties applicable to a globe goordinate (see here). See for instance this query, which retrieves, for Berlin, the latitude, longitude and globe (Earth, of course):
Extended content
:
select * where {
  wd:Q64 p:P625 / psv:P625 [
    wikibase:geoLatitude ?la ;
    wikibase:geoLongitude ?lo ;
    wikibase:geoGlobe ?globe ;
  ] .
}
Try it!
Now one can turn this around and ask for items on, say, Mars:
select * where {
  ?item p:P625 / psv:P625 [
    wikibase:geoLatitude ?la ;
    wikibase:geoLongitude ?lo ;
    wikibase:geoGlobe wd:Q111 ;
  ] .
  ?item rdfs:label ?label . filter (lang(?label) = "en")
} limit 5
Try it!
Best wishes, Toni 001 (talk) 09:58, 21 December 2021 (UTC)[reply]
  • @Paperoastro: In some applications, it's indeed possible to filter out such coordinates for some planets/objects, provided that current settings of the Query Server allow it and there are not too many involved. This however is more complicated, if not impossible if you want to have Earth coordinates (see previous discussion). I don't think we have seen a valid usecase for having coordinates any planet in the same property. --- Jura 11:51, 22 December 2021 (UTC)[reply]
@Paperoastro: I've changed my opinion on this proposal. Mars is a significant enough planet that it merits its own property, so I  Support making a "Martian coordinates" property. I still think we should make a generic property at some point, however, for asteroids, fictional planets, etc. — The Erinaceous One 🦔 16:05, 23 December 2021 (UTC)[reply]
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