[Discuss] OpenStreetMap in Victoria

[Nick Black]

On 7/30/07, pw <p.willis at telus.net> wrote:
> Corey Burger wrote:
> >>         I'd be interested in helping out, but I don't have a GPS unit. What I
> >> can do is cycle around if someone was able to provide the GPS unit. I'm
> >> not as fast as a motor vehicle, but I am (obviously) eco-friendly. :D
> >
> >
> > A few months back, Yahoo lent their Aerial Imagery to OSM for the
> > tracing over. As such, you don't need a GPS to contribute. I have in
> > fact traced over most of the roads in Victoria, Oak Bay and Saanich.
> >
> > Corey
>
> Are you using a projection or just latlon for
> your reference system?

The OSM database stores coordinates in latitude and longitude,
according to the WGS84 datum.  WGS84 is a global reference system, so
its an approximation of the earth that attempts to be not-too-bad
anywhere on the earth,

>
> I was also curious about the best method for doing
> road segments. It was my thought that segments should
> be kept as separate vectors. This allows shortest route
> selection and driveway geography for locales rather than
> having one huge vector for everything. Attributes
> don't tend to help with data reduction that way unless
> the segment geography is part of the attributes of each
> entity.

If I understand your question correctly, the current best practice, is
to tag (assign attributes to) ways. Ways are collections of continuous
segments, which are stored in the db as an ordered list of segment
ids.  The end user sees this as attributes being attached to a road,
but in reality, the db has seperate tables for tags and segments.

If you want to know more about this sort of stuff, its probably best
to ask on the dev@ mailing list.  Its always worth remembering with
OSM that there is a lot of 'best practice' that is defined by the
community, but not enforced by the data model or the API.

Best,

>
> Peter
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-- 
Nick Black
--------------------------------
http://www.blacksworld.net