[OSM-dev] area filtering on change streams?

Frederik Ramm frederik at remote.org
Mon Jan 21 07:00:43 GMT 2013


On 01/21/13 07:54, Brian Cavagnolo wrote:
> I'm kinda hooked on the appeal of only working with the changeset.  I
> poked around the osmosis source and learned a bit about the change
> format.  It looks like changes could be filtered using the same code
> used for the polygon and bounding box filters.  Does this sound
> intuitively correct?


The fact that changesets cannot be filtered by region is not a software 
limitation, it is a design limitation.

Changes can occur in nodes, ways, or relations; but only nodes have a 
geometry given in the .osc file. For example, an .osc file might contain 
the information "way #17 has been changed from highway=residential to 
highway=unclassified" but you won't know if that is relevant to you 
because the nodes of that way are not included in the changeset (unless 
by chance they have been modified at the same time).

If you really want to pursue this further, read up on "augmented diffs" 
which are reference-complete and would therefore allow such filtering: 


Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"

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