At 2010-12-19 02:21, Wyo wrote:
Alan Mintz wrote:
At 2010-12-19 00:59, Wyo wrote:
I've just realised that rather many nodes have their own source tag, even
if they are just part of a way with identical tag. So I guess a rather
large part of the data consists of these source tags. While this isn't a
problem for files (thanks to compression) it enlarges the database quite
a bit.
Are these tags really necessary or could they be remove as long as the way
has a source tag? Could anybody provide an estimate how much space
reduction could be gained? Could anybody create a report on how many nodes
have identical tags as their way?
Do you have an example?
See http://www.openstreetmap.org/edit?lat=47.17473&lon=4.71559&zoom=17
where the nodes of the canal way have identical values.
Oddly, only some of them. I agree that these seem duplicative (and I don't
see the need for such a long value, where cadastre_2009 would convey the
same info).
I tag intersections of ways as I survey them with source=*, source_ref=*
among other things, like signalling, turn restrictions, etc. Sometimes, the
source value is the same as that of the way, but that is only coincidental
- it's not a duplication.
Sorry I don't understand that. Since nodes obviously inherit (by
understanding) anything from their ways, the values either must be
different to show different info or they don't carry any info.
I don't agree that they necessarily inherit from their ways. A node along a
street is not named, not functionally classified (i.e. highway=primary), etc.
The situation I was referring to was this:
I tag a street: { source="survey;image;usgs_imagery" +
source_ref="AM909_DSCN1234" + name="Foo Street" } after tracing it from
satellite imagery, then surveying it and taking a pic of the street sign
(id'd by the source_ref) somewhere along the way.
Somewhere along this same street may be a node tagged {
highway="traffic_signals" + source="survey;image;yahoo_imagery" +
source_ref="AM909_DSCN5678" } indicating that I surveyed it, took a pic,
and positioned the intersection according to (different) satellite imagery.
While the two may share the survey;image sources, that is only
coincidental, not duplicative. There may be other nodes along the way that
I have not surveyed or taken pics of, which do not have tags.
--
Alan Mintz <[email protected]>
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