On 10/04/11 17:47, Jochen Topf wrote:
GET http://api.openstreetmap.org/api/0.6/node/1/history tells me this:
<osm version="0.6" generator="OpenStreetMap server">
<node id="1" lat="2.0" lon="2.0" changeset="9257" user="τ12" uid="1298" visible="false"
timestamp="2006-05-10T18:27:47Z" version="1"/>
<node id="1" lat="50.1249473" lon="14.4557581" changeset="196013" user="tacut" uid="113502"
visible="true" timestamp="2009-04-04T10:01:54Z" version="2">
<tag k="name" v="Metro C - Kobylisy"/>
<tag k="wheelchair" v="yes"/>
<tag k="railway" v="subway_entrance"/>
</node>
<node id="1" lat="2.0" lon="2.0" changeset="524633" user="woodpeck" uid="5164" visible="true"
timestamp="2009-04-14T15:42:57Z" version="3"/>
<node id="1" lat="2.0" lon="2.0" changeset="1767082" user="Ldp" uid="48796" visible="false"
timestamp="2009-07-07T22:44:41Z" version="4"/>
</osm>
How exactly am I to interpret this? Why are some visible="true" and some
visible="false"? The visible="false" on the last version tells me the node
is deleted. But what happened before? Does the visible="false" on the first
version mean it was deleted before it was re-created as version 2? For a
deleted node, does the timestamp refer to the creation or the deletion?
Here goes...
The real node 1 should be somewhere in the Regents Park area of London
but it has a history of being accidentally changed by badly written
imports and bots which just make up IDs starting at 1 and things.
It looks like in May 2006 it was deleted - it was already at a silly
location so had probably already been the victim of a rogue client. We
have no history before that online because history was wiped when we
went to api 0.5 in October 2007.
It was then resurrected by somebody uploading a valid node 1 in April
2009 (just a few days before api 0.6 went live with version checks to
make these accidental overwrites harder).
Frederik obviously noticed this and reverted that changeset, moving the
object back to it's previous position again but not actually marking it
as deleted. Eventually Lennard came around and deleted it again.
If you look at changeset 196013 you'll see it is just an upload of nodes
1 through 17 so a classic bad import. Those 17 nodes are then moved back
again in Frederik's changeset.
Tom
--
Tom Hughes ([email protected])
http://compton.nu/
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