The 9 digits precision was based on a survey of Wikipedia we did back then
and the most precise GPS coordinates in Wikipedia. Unfortunately, I don't
remember anymore what article it was - it was some article listing a number
of places that have, due to whatever reason - really high precisions. If
someone finds the article again, I would be thankful. It might help in this
conversation. The 9 digits were not chosen arbitrarily, but based on the
requirements from Wikipedia.
But, this is just the most detailed precision. In most cases, as you
notice, we won't need this high precision, but we will have a much lower
precision. Pinning down a municipality with a 9 digit precision is
obviously nonsense. For most countries, any precision beyond 0 seems quite
But that's also true for time. The time data model allows to
second-precision, but obviously, for much of the data that does not make
sense. Nevertheless, the datamodel supports saving it, we don't want to
loose here compared to the base data.
I am not sure I understand the issue and what the suggestion is to solve
it. If we decide to arbitrarily reduce the possible range for the
precision, this still won't lead to any improvements for countries as
compared to statues. As far as I can tell, the only way to actually solve
this is to provide query patterns that take the precision into account and
to have the system implement it correctly.
On Thu, Aug 31, 2017 at 2:38 PM Stas Malyshev <smalyshev(a)wikimedia.org>
I think that should be 5 decimals for commercial
GPS, per that link?
It also suggests that "The sixth decimal place is worth up to 0.11 m:
you can use this for laying out structures in detail, for designing
landscapes, building roads. It should be more than good enough for
tracking movements of glaciers and rivers. This can be achieved by
taking painstaking measures with GPS, such as differentially corrected
This does not seem to be typical (or recommended) use case for Wikidata.
If you need to build a road, you better have some GIS database beyond
Wikidata I think :)
Do we hope to store datasets around glacier
movement? It seems
possible. (We don't seem to currently
I skimmed a few search results, and found 7 (or 15) decimals given in
one standard, but the details are beyond my understanding:
Note that there's a difference between what general GIS standard would
require (which has much more use cases), what we want to store on
Wikidata and what we want to use for RDF export and querying. The latter
is of more concern to me - as overprecision there might actually make
things a bit harder to work with (such as - "are these two things
actually the same thing?" or "are they located in the same place?") Of
course, all those problems are solvable, but why not make it easier?
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