On Sat, May 7, 2011 at 6:31 PM, Lmhelp <[email protected]> wrote:
> Hi again,
>
> I just want here to put things a little bit clearer (I am a beginner, I
> hope it won't be too confused).
>
> I have:
> - a GeoServer layer L1 which data come from a PostGIS table T1
> containing geometries of type "POINT" (points),
> - a GeoServer layer L2 which data come from a PostGIS table T2
> containing geometries of type "MULTIPOLYGON" (French departments),
> - a GeoServer group of layers G containing these two layers L1 and L2.
>
> As a result, I want to display a map "containing" those two layers
> (using OpenLayers).
>
> I need to compute a bounding box FROM these data ((T1 and T2) or (L1 and
> L2) or (G)).
> I need to do this programmatically.
> The bounding box I'll get as a result has to fit exactly the displayed
> data, in my case a map of France with "points" on it.
>
> The bounding boxes computed by Geoserver in my case are (for both T1 and
> T2):
> +--------+-----------+-----------+-----------+
> | Min X | Min Y | Max X | Max Y |
> +--------+-----------+-----------+-----------+
> | 99,226 | 6,049,647 | 1,242,375 | 7,110,524 |
> +--------+-----------+-----------+-----------+
> => I don't understand what these huge numbers are (what is their unit of
> measure, etc.)...
These come from asking PostGIS directly. Depending on how you setup
the store they might be the result of:
select AsText(force_2d(Envelope(ST_Estimated_Extent('schema', 'table',
'column')))
or
select ST_AsText(ST_Force_2D(Envelope(ST_Extent(column)::geometry))))
from schema:table
where you have to replace schema, table and column for your specific case
and be lenient since I've derived the queries from the code but did
not have time to
try them out (parenthesis might not be balanced and the like).
The first query is run if you enabled "estimated extent" in the db, and uses the
spatial index statistics to compute the bbox quickly, the second is run if the
first fails or if estimated extent is not enabled, and does a full
scan of the table
and computes an exact bounding box.
By the numbers you get it seems your data is in some projected
coordinate system.
Which one, I cannot know.
Cheers
Andrea
--
-------------------------------------------------------
Ing. Andrea Aime
GeoSolutions S.A.S.
Tech lead
Via Poggio alle Viti 1187
55054 Massarosa (LU)
Italy
phone: +39 0584 962313
fax: +39 0584 962313
http://www.geo-solutions.it
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http://www.linkedin.com/in/andreaaime
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