So you want to e.g. give the height of a bridge above the "mean high water spring" level of the river it crosses? You wouldn't use a unit for that, but a qualifier. The unit would be meter (or feet or whatever). The "elevation" property we have (P2044) is defined to refer to NN, so it's no good for your purpose. To model what you want nicely, you would need a more general "elevation" property, and a "reference level" property to use as a qualifier. Then you could express something like "elevation: 28.3m; reference-level: Q6803625". I'm sure there are other options, but I see no good option that would be possible with the properties I know. Anyway, this is really a modelling question, and it can't really be solved with units. Am 27.09.2016 um 20:26 schrieb Markus Bärlocher: -- Daniel Kinzler Senior Software Developer Wikimedia Deutschland Gesellschaft zur Förderung Freien Wissens e.V.

Hi Daniel, Markus and Wikidatans, Thanks for your interesting "modeling elevation with Wikidata" conversation. Daniel, in a related vein and conceptually, how would you model elevation change over time (e.g. in a Google Street View/Maps/Earth with TIME SLIDER, conceptually, for example) with Wikidata, building on the example you've already shared? For example if one wanted to use Wikidata to model the 9 levels or 46 sublevels of Troy (https://en.wikipedia.org/wiki/Troy) and when they were excavated and how (so a time horizon with a place horizon), how would one do so? (On behalf of CC WUaS I'd like to explore facilitating doing this eventually in a realistic virtual earth, something like Google Street View/Maps/Earth with time slider with OPEN SIMULATOR, conceptually, and as a World Univ & Sch "classroom" and as a way, for example, for archaeologists and related scientists to add each of their own videos and photographic data, say, from all of their digs in 1910 of level X and contrast this with each of all of their own videos from level Y in 1958 (if digs were happening in these years) - https://radalma.wikispaces.com/file/view/troy-the-nine-periods-of-troy-cros… (e.g. https://radalma.wikispaces.com/Timeline+of+Troy) - with great STEM precision of time and place elevation, - and also in ANY language, so involving Wiktionary and translation?) Would there be a wikidata Q-item for all 46 sub levels, for example? Thank you. Bests, Scott On Tue, Sep 27, 2016 at 1:21 PM, Markus Bärlocher < markus.baerlocher(a)lau-net.de&gt; wrote: -- - Scott MacLeod - Founder & President - http://worlduniversityandschool.org - 415 480 4577 - PO Box 442, (86 Ridgecrest Road), Canyon, CA 94516 - World University and School - like Wikipedia with best STEM-centric OpenCourseWare - incorporated as a nonprofit university and school in California, and is a U.S. 501 (c) (3) tax-exempt educational organization. World University and School is sending you this because of your interest in free, online, higher education. If you don't want to receive these, please reply with 'unsubscribe' in the body of the email, leaving the subject line intact. Thank you.

Am 27.09.2016 um 22:21 schrieb Markus Bärlocher: Yes, I agree. But that's how it currently is. You can start a discussion about it on the property's talk page, or on the project chat page, or some other appropriate place. As far as I know, WD uses "altitude" only as an alias of "elevation". I'm not a native speaker of English, but as far as I know, you can use "altitude" as well as "elevation" when describing a geographical point. The definitions of the corresponding items (Q190200 and Q2633778) reflect that, and so do the definitions in Merriam Webster. However, "elevation" seems to be used only for fixed places - a plane has altitude, not elevation - so that's a reason not to merge the two items. However, if I understood correctly, what you are looking for is actually not elevation, but "clearance" ("Lichte Höhe"): <https://www.wikidata.org/wiki/Q1823312>. Interestingly, there is also Q2446632... Oh, we actually do have a property for that! P2793 is the "distance between surface and bottom of a bridge deck". That's exactly what you need, no? Indeed :) And a civil engineer. But for starters, maybe Aude has some thoughts on this. Sources can be given for any statement. Accuracy can be qiven for any quantity value, just enter 32+-2m. If the source gives the number in feet, please enter it in feet in Wikidata, and leave the conversion to the software (we are just in the process of adding support for unit conversion) HTH, Daniel PS: I'm a software guy. I know how Wikibase and MediaWiki work, and I know the underlying data model of Wikidata quite well. But I do not know all the properties and conventions, and I may not be aware of the best place to discuss these things. So please don't rely on my opinion about modeling on Wikidata too much. -- Daniel Kinzler Senior Software Developer Wikimedia Deutschland Gesellschaft zur Förderung Freien Wissens e.V.

Am 28.09.2016 um 14:13 schrieb Markus Bärlocher: "Die Community"... Die Referenzebene kann wie gersagt als Qualifier angegeben werden. Es wäre sinnvoll, die Property "Elevation over sea level" entsprechend umzudefinieren oder zu ersetzen. Eine andere Lösung fällt mir nicht ein. Es sei denn, es geht um "Lichte Höhe", dann kannst du P2793 benutzen. Du brauchst aber immernoch eine Property für "Reference level". Ich glaube, die gibt es noch nicht. Ja, genau so. Oder so ähnlich - bei der Eingabe muss die Einheit momentan noch separat ausgewählt werden. Nein, das ist ja kein Text-Feld. Wert, Genauigkeit, und Einheit werden separate gespeichert, dafür haben wir "data types." Details findest du hier: <https://www.mediawiki.org/wiki/Wikibase/DataModel/JSON#quantity> und hier <https://www.mediawiki.org/wiki/Wikibase/DataModel#Quantities>. -- Daniel Kinzler Senior Software Developer Wikimedia Deutschland Gesellschaft zur Förderung Freien Wissens e.V.