[OSM-talk-ie] Newbie!

Dermot McNally dermotm at gmail.com
Mon Mar 17 01:29:53 GMT 2008


Hi Andrew, and welcome...

On 16/03/2008, Andrew McCarthy <me at andrewmccarthy.ie> wrote:

>  1) Is there a way to classify narrow tertiary roads, as opposed to
>  "normal" width ones? On Ordnance Survey maps these would show up as
>  skinny yellow roads.

This may depend a little on what you understand a tertiary road to be.
If you haven't already seen it, you may wish to refer to the tagging
guidelines for Irish roads:

http://wiki.openstreetmap.org/index.php/WikiProject_Ireland#Highway

(disclosure: I wrote this, it has, like all other OSM documentation,
no official standing, but it ties in closely to what the UK mappers
are doing and it makes for reasonable rendered output).

There has been a lot of confusion in the community about what tertiary
is supposed to mean, but I've generally used it to represent a road
that you'd cheerfully use on a route to somewhere even if your
destination wasn't actually on that road.

To return to your question, therefore, I'd imagine that overly narrow
roads wouldn't be ones you would use by choice as a route to somewhere
and for that reason I'd tag them as unclassified, not tertiary.

>  2) Some of the existing roads seem to have far more nodes than
>  necessary, for example a dozen in 100 metres that's dead straight. In
>  some places this also leaves the road in the generated map a bit
>  "rippled". Is it a good idea to clean up some of these roads?

It can be. JOSM has a plugin that can do this for you, based on an
"aggressiveness threshold" that you can customise yourself. So if
you're going to do it, you'd probably be foolish to do it laboriously
by hand. But you should probably take pains to ensure you're not
discarding any good information. A rippled road can mean too many data
points (if it's rippled at very high zoom level) or it could mean far
too few points (if rippled at lower zoom - in this case, the points
you have are useful, but insufficient to convey the true detail of the
bends). You should probably refer to a good-quality GPS trace during
any cleanup you undertake to avoid junking useful detail.

Happy mapping!
Dermot




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