[Talk-us] directions of ways in MassGIS data

Christopher Schmidt crschmidt at metacarta.com
Sun Feb 1 16:01:15 GMT 2009


On Sun, Feb 01, 2009 at 10:55:56AM -0500, Greg Troxel wrote:
> 
> Christopher Schmidt <crschmidt at metacarta.com> writes:
> 
> > MassGIS does not encode the direction. Oneways which are potentially
> > wrong are marked with a FIXME note to fix the incorrect directionality.
> > (I believe it is 'FIXME: Unconfirmed oneway'.) MassGIS pays NavTeq for
> > routing data, and does not have a 'free' source of Oneway
> > directionality. 
> 
> OK, so it's either manual, or having something that looks at the db and
> finds pairs of ways tagged as motorway/primary/secondary that go the
> same way and are labeled FIXME and flips on of them, assuming they are
> laid out normally, changes FIXME tag to auto-fixed, and then maybe
> propagates this to ramps.  That sounds like a fair bit of work, maybe
> more than hand editing them all.

It's also not just motorways -- that's just the most obvious. ALl of
Cambridge/Somerville has been done by hand, and the same will be true of
most other towns that have one way roads inside of them. The
split-directions roads are a case which is solvable technically, but
since so many others aren't, I've always ust figured it'll get changed
when peole go through the rest of the roads in an area.  

> > The classifications are based on the roads data, which is maintained by
> > the executive office of transportation. I would assume that the
> > classification is based on the legal classification of the road, rather
> > than on usage.
> 
> OK, so it's then proper in osm terms to adjust it to the usage/physical
> method?  Would you call 2 from alewife to 128 a motorway?  (I'm just
> checking my understanding of the norms before making changes.)

I don't know. I just import data, I've never mapped anything out. :)
Others might be able to comment on it more. Generally speaking, I'd
probably refer to that stretch of road the same way I would to an
interstate; I don't know what that translates to, but changing it to
match that makes sense to me.

-- Chris

> (For those not in MA, here's an example interchange on this highway
> 
> http://www.openstreetmap.org/?lat=42.42188&lon=-71.23007&zoom=16&layers=B000FTF
> )



-- 
Christopher Schmidt
MetaCarta




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