[OSM-dev] idea: before-after map

Martijn van Exel m at rtijn.org
Mon Dec 5 18:11:11 GMT 2011


Thanks,

For it to work (for current changesets) though, we would need a
continuously updated full history database..

On Mon, Dec 5, 2011 at 10:46 AM, Peter Körner <osm-lists at mazdermind.de> wrote:
> Am 05.12.2011 18:08, schrieb Martijn van Exel:
>
>> Hi,
>>
>> Now that we have the history files and a history renderer in the
>> making [1] it would be possible to create a Before / After service:
>> user would select one or a few concurrent changesets comprising an
>> edit session, and the service would churn out a pretty HTML page with
>> a static map of the area just prior to the changesets affecting the
>> area and just after the last ones were closed.
>>
>> I was just wondering how difficult / feasible this would be to
>> implement. Do we even need Peter's renderer for it?
>
>
> You could use the database and the valid_from / valid_to processing used in
> the views to get the before/after state and do whatever you want (ie compare
> version & minor version to find affected items).
>
> Just use this clause in your where-statement to get all items at this point
> in time:
> '2010-01-01' BETWEEN valid_from AND COALESCE(valid_to, '9999-12-31')
>
> Take a look at render.py to see how it's used.
>
>> [1] https://github.com/MaZderMind/osm-history-renderer
>
>
> Peter
>
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martijn van exel
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