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

Frederik Ramm frederik at remote.org
Tue Dec 11 10:02:58 UTC 2018


On 11.12.2018 10:37, Tomas Straupis wrote:
>   1. Non-physical objects are mapped by observing/verifying their
> REFLECTION in physical world.


>   Opinion 1 would mean that we should remove all(most?) non-physical
> objects: country, state, county, city, suburb, national/regional park
> boundaries (and a lot more) as most of that is unobservable on the
> ground and sometimes reflection of small part of them on the ground is
> misleading/outdated.

I think that we should not have a "fundamental" approach here but one of

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.

For example, certain historic facts are very well documented, sometimes
even by old maps or photographs, but we don't want them in OSM if they
are not visible on the ground any more. I think that this is the right
approach, and we normally don't want things that are not visible on the

We are making an exception, though, for some types of boundaries because
we think they are important enough to warrant this exception. Not only
important for map users, but also for the mapping process itself - for
example, boundaries could be important for our own statistics or for
knowing whether or not you are even allowed to go somewhere.

"Let's delete all boundaries" would certainly be an overreaction; "let's
require a very good reason for boundaries to have them in OSM" is
better. But "let's map things according to documents" is IMHO worse, and
you haven't even touched on the question of authority (whose documents
do you believe). You are right in saying that most current boundaries in
OSM are actually copied from documents, but we only do that where
everyone agrees that the documents actually depict the situation on the
ground. As soon as they are out of touch with the situation, we won't
consider documents a useful source any more.

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.


Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"

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