[OSM-talk] Very long ways
osm-list at deelkar.net
Wed Mar 28 13:08:05 BST 2007
-----BEGIN PGP SIGNED MESSAGE-----
Mike Collinson schrieb:
> At 02:17 PM 28/03/2007, Lars Aronsson wrote:
>> Are there any guidelines for how long ways should be? Either by number of segments or by geographic size? >
> More generally from my editing rather than rendering or technical db
> point of view:
> Number of segments: Probably irrelevant? The more, the slower it
> is to download. If they are in your current edit area, you still
> need to download them whether it is one or several ways. If they
> extend outside your area, it is pointless to download them but the
> crucial factor is the geographic size, not the number.
I agree, the segment count is only a measure how painful it will be to
download the way if it's incomplete.
> Geographic size: The bigger, the more statistically likely the way
> will be incomplete in any given edit and cause problems.
> I came up with 12km for long distance features such as railways and
> 1.5km for urban ways.
I thought about this as well and came up with a very similar number.
> 1.5km seems good but 12km too small for countries like Canada and
> Australia. Doubling the allowed OSM download area would give 24km,
> which might allow a way break at the next turn-off or bridge and
> would allow for less crowded labelling on 1:250,000 and 1:500,000
There is no problem when creating the way to create it as one long, 1500
km (or whatever length) way, tag it and then splitting it up.
(preferably before upload)
> I'd should say the rough guide is about half the geographic width of
> the JOSM window when you do your initial download (a sort of Nyquist
> At the moment OSM won't let me download if the slider is set to over
> 2.1 km, so that gives me 24 km of window so 12km optimum length.
the api restricts the bounding box an area equivalent to 0.3*0.3
degrees. This means you can, if you have a looong east-west road in
Australia perhaps, manually edit the bbox for the request to be 0.01*9
degrees in size.
> When dealing with 500km roads I find that a pain in the behind.
> Allowing double the download window for working in sparsely populated
> areas of the world would allow 24km, not great but workable.
As stated above, create the way in one long piece, then split at
bridges, onramps or whatever.
> I'd say 24km max and preferably half that, 12km, would be good in
> sparsely populated areas and for long distance features such as
> railways and motorways. 24 km is roughly the width of a JOSM screen
> when the slide bar is set to 2.1km, the maximum that you can download
> from OSM at them moment.
> For dense urban areas where your edits are probably going to be very
> local and you don't want to download the whole city, I tend to
> download with the JOSM slider set to 263m --> 3km window --> 1.5km
> way length.
For motorways (which are the roads in Germany that run the real
distances) I split them at every "important" exit outside, and at
*every* exit inside urban areas, resulting in something like 10-40 km
outside and 2-5 km inside urban areas.
(The former is not really optimal, but given the low node density on
motorways due to their not-too-curvy layout, still manageable.)
Dirk-Lüder "Deelkar" Kreie
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
-----END PGP SIGNATURE-----
More information about the talk