[Talk-us] Re: Boundaries and verifiability (was Re: Retagging hamlets in the US)

[Minh Nguyen]

On 2015-03-25 08:12, Martijn van Exel wrote:
> On Wed, Mar 25, 2015 at 3:00 AM, Minh Nguyen wrote:
>
>     On 2015-03-24 13:57, Martijn van Exel wrote:
>
>         More importantly though, there is an authoritative source for
>         official administrative boundaries that can be easily accessed by
>         anyone: TIGER[1]
>
>
>     You mean the way TIGER is an authoritative source for road
>     centerlines? TIGER's boundaries vary in quality just as its roads
>     and railroads do. I've taken quite a few imported municipal
>     boundaries, lined them up with road easements or hedges between
>     farms _when that is obviously the intent_, and deleted extra nodes.
>     These borders become far more accurate and precise in OSM than in
>     commercial maps, which regurgitate TIGER boundaries verbatim.
>
>
>     The most authoritative source for most U.S. land borders, going all
>     the way down to the parcel level, is a legal prose definition in
>     conjunction with any number of monuments on the ground. Both metes
>     and bounds and the Public Land Survey System rely on monumentation.
>     A monument may be a major road or as obscure as a small iron pin
>     embedded in that road, but even that pin is verifiable if not
>     particularly armchair-mappable.
>
>
>     If you're lucky, you can find an Ohio city limit's legal definition
>     in county commissioners' minutes when an annexation is proposed. The
>     most authoritative data representation is the county GIS database,
>     which anyone can easily access -- for a fee. After paying the county
>     for that database, you might well forget about OSM, because it's
>     also the authoritative source for road centerlines and names.
>
>
> That is actually not what I meant, but I could have been more precise. I
> guess this turns into a discussion of what 'authoritative' actually
> means. This is different things to different people. As OSM becomes
> better, increasingly folks will start looking at us for
> authoritativeness, which would make sense because everything is
> (supposed to be) verified on the ground. Because administrative
> boundaries have legal implications, the authoritative source will need
> to be someplace outside of OSM. It may actually hurt OSM down the line
> if we include information that suggests authoritativeness we cannot
> provide.

OK, thanks for clarifying. One risky use of administrative boundary data 
at the local level would be for tax purposes. Obviously we don't want 
people relying on OSM to decide whom to pay taxes to. That's why we have 
a disclaimer. [1] It should get more prominence. Wikipedia's legal and 
medical disclaimers are two hops away from every article, but ours is 
two hops from the wiki's main page only. At least consumer-focused 
redistributors of OSM data tend to have more accessible disclaimers.

[1] http://wiki.osm.org/wiki/Disclaimer

> Sure, but vernacular and official neighborhood objects would then need
> to be represented differently so folks can tell them apart and know what
> they are dealing with.

I agree entirely, and I think OSM is already set up for these 
distinctions. If you see a boundary=administrative admin_level=10 
relation on the map, you'd expect it to be an official (aka 
administrative) boundary, not a vernacular one. If you see a 
place=neighborhood POI with the name tag, you'd expect both definitions 
to be roughly equivalent. A purely vernacular neighborhood would be a 
POI probably tagged with loc_name instead of name.

-- 
minh at nguyen.cincinnati.oh.us