[OSM-dev] OSM History Retriever

Brett Henderson brett at bretth.com
Fri Jul 23 13:20:42 BST 2010


On Thu, Jul 22, 2010 at 6:14 PM, Martijn van Exel <mvexel at gmail.com> wrote:

>
> On 22 jul 2010, at 06:57, Brett Henderson wrote:
>
> On Wed, Jul 21, 2010 at 11:52 PM, Lars Francke <lars.francke at gmail.com>wrote:
> [...]
>
> That format is fine and exactly what I would have expected.  I suspect
> Osmosis would parse it okay, but without support for the visible attribute
> it won't be particularly useful.
>
>
> Not for visualization purposes maybe, but for analysis purposes the visible
> attribute is not really an issue. My goal is to extract full history dumps
> for certain spatial extents and import them into a PostGIS, in order to
> calculate historical metrics exposing the crowd dynamics of OSM - for
> example number of contributors over time, version growth over time, movement
> of nodes over time. All this calculated for grid cells.
>
> The full history dump is 13GB bz2 compressed. Anyone got a rough idea how
> long it would take for osmosis to extract, say, a bbox of the Netherlands
> out of that on a 4GB AMD Opteron quad core machine? More RAM would probaby
> help?
>

Osmosis is unlikely to work well on a full history dump.  The --bounding-box
task is really only designed to work with data from a single point in time.
Data across a time range is much more difficult to accurately perform
bounding box filtering, although it might be good enough.  A bigger issue is
that it will ignore visible attributes and strip those attributes from the
output.

A relatively small amount of RAM is used for a single --bounding-box task if
you specify the idTrackerType=BitSet option.

Brett
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