[Imports] Administrative Boundaries and Divisions in Portugal

[Christoph Hormann]

On Tuesday 14 April 2015, you wrote:
> >
> > * definition through point coordinates and geodetic lines between
> > * definition through physical geographical features like rivers or
> > ridges
> > * definition through a mathematical formular based on either
> > coordinates or physical features - this is primarily for maritime
> > boundaries.
>
> and a fourth (perhaps not true for international boundaries): town
> boundaries in Massachusetts are primarily defined by granite markers.

I included those in the first category.  Usually such markers are placed 
by a survey team after the boundary has been negotiated.

The problem is over time marker and measured coordinates can differ - 
either through physical movement of the marker or through movement of 
the earth surface relative to the coordinate system used.

If the markers are relatively new it is safe to assume that for 
practical purposes they are the authoritive definition.  If however the 
markers get very old (here in Germany on a municipal level they are 
frequently over a hundred years old) this gets questionable.  Anyway 
many boundaries in OSM are much worse so it would already be a great 
improvement to move them to the existing markers.

> But regardless, I think OSM is a great place to curate boundary
> information, where "verfied" includes not only visiting markers
> (unsurprisingly, all the ones i've visited have been where the state
> dataset says they are), but also looking up the law and the things
> the law references.

Yes, such information is often difficult to find but this would be a 
good opportunity for OSM.

-- 
Christoph Hormann
http://www.imagico.de/