[OSM-talk] Ground truth for non-physical objects

[Tomas Straupis]

2018-12-11, an, 12:06 Frederik Ramm rašė:
> Non-physical (non-observable) things should definitely be the exception
> in OSM, and it is my opinion that each class of non-physical things we
> add needs a very good reason for adding them.

  I agree, but that is a different question. My suggestion is to
discuss this later as a separate topic so that initial question of
"what ground truth means" would not be buried. We could later have
either (preferably) a criteria, or (if criteria is not possible)
simply a table listing acceptable or not acceptable non-physical
objects in the database.

> Also, I think you are too fast in discounting the verifiability of
> boundaries. Even in the absence of actual marked lines, fences, or
> walls, you will often find the "reflections" that you speak of if you
> look a bit closer: Which government do I pay my taxes to? Which police
> department is responsible for my area? Which local authority do I get my
> food stamps from, whatever.

  Well, the first thing is to decide if boundaries as non-physical
objects originate in documents, or physical observation and which one
we use. Mixing those is what is introducing subjectivity and thus
different interpretation and problems.

  Then we can decide on priorities (if required at all). For example
for all boundaries (except country boundaries) there is a clear
candidate - local authority (government for administration division to
states, counties, cities, suburbs etc.), same local authority or some
national park administration whoever is deciding on official
boundaries of national/regional parks, protected areas etc.
  I cannot think of an example, where some important object worth
being in OpenStreetMap database would not have a single authority
deciding on its geometry.
  And this could work with country border only if we accept the
possibility of overlapping borders (which sometimes do exist even
without conflicts between countries).

  Tax, police does not look like a firm criteria because:
  1. You would need some documents to verify that anyway?
  2. Tax/police regions do not necessarily correspond to
administrative divisions and they could differ/overlap.

  Note that while it is relatively easy to spot a missing non-physical
object and then add it, it is much harder to notice a change of it. If
we would agree on using official documents it would allow to do such
checking by local community regularly (which does not necessarily mean
updating the data automatically by import, this could simply raise a
flag "please check here"). This is what is done in "some" countries
currently with ALL sides getting benefit and thus being a very good
selling point for OSM and now it is very disturbing to find it is
"against the old standing rules" :-)

-- 
Tomas