[OSM-dev] OSM PBF and spatial characteristics of blocks
Benjamin.Stadin at heidelberg-mobil.com
Tue Jan 5 16:43:01 UTC 2016
One more question:
4) The documentation says: "The current serializer (Osmosis<http://wiki.openstreetmap.org/wiki/Osmosis>) preserves the order of OSM entities, and tags on OSM entities."
What would be the downside if this order was lost (when the FileBlocks are recreated in a custom spatial order)?
Von: Benjamin Stadin <benjamin.stadin at heidelberg-mobil.com<mailto:benjamin.stadin at heidelberg-mobil.com>>
Datum: Dienstag, 5. Januar 2016 um 17:32
An: "dev at openstreetmap.org<mailto:dev at openstreetmap.org>" <dev at openstreetmap.org<mailto:dev at openstreetmap.org>>
Betreff: [OSM-dev] OSM PBF and spatial characteristics of blocks
I’m thinking about a design for an efficient storage container for OSM PBF (planet size data, minutely updates), for the purpose of TileMaker as well as for an internal application.
One thing I stumbled on is the usage of the bounding boxes within OSM PBF. The documentation  does not clarify on the spatial characteristics of the individual FileBlocks. Some questions:
1. Is it correct that there is exactly one HeaderBlock in a .pbf file? If so, the BBOX defined within the HeaderBlock defines the whole region of the .pbf export?
2. What are the spatial characteristics of an individual FileBlock within the FileBlocks sequence? Is a FileBlock generated by any kind of spatial ordering? For example, is it save to assume that all content is very dense / close to a region of the world? Or can this be controlled when creating a .pbf? If there was a spatial loose relationship, it would allow to relate FileBlocks to map „tile“ regions (a FileBlock may obviously relate to several „tiles“, but would be fine as long as the blocks relate to a certain region for most of it’s content)
3. There is a commented BBOX definition within the PrimitiveBlock. What remains to be done to to enable this proposed BBOX extension? I’d have the same question about this BBOX as with my second question.
// Proposed extension:
//optional BBox bbox = 19;
I’d add an additional parse step to create this spatial relationship, if there is no spatial relationship yet or the spatial characteristics are not „good enough“.
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