[postgis-users] AsKML() how to create kml from postgis data

[Shane Spencer]

http://www.bostongis.com/PrinterFriendly.aspx?content_name=ogr_cheatsheet

I use ogr2ogr for doing that..  however sometimes its best to write the KML
using your own structure, descriptions, and element names.

http://www.gdal.org/ogr/drv_kml.html will describe the options that let you
name the KML elements based off of a database fields data.

On 9/14/07, Dylan Beaudette <dylan.beaudette at gmail.com> wrote:
>
> On Friday 14 September 2007, John Smith wrote:
> > as_kml()?! there's another askml() in line with asgml(). why this
> > alias/name change/confusion?
> >
> > anyway how does it really work? getting a "Must contain
> > 'geometry_column from table_name' or 'geom from (subselect) as foo'
> > (couldnt find ' from ')". what do i do after passing bbox=... and
> > type=kml to export script? the sql doesn't go inside .map, right? can
> > some share a detailed use/script? not much in
> > http://postgis.refractions.net/docs/postgis.pdf
>
> I'll add a bit to this discussion, as I have tackled it before.
>
> > btw super example at
> >
> http://casoilresource.lawr.ucdavis.edu/ka-map/htdocs/?map=casoil&cps=-20125
> >07.9410234897,-132997.150403761,500000&layers=__base__
>
> Thanks! Here is a shorter link to the corresponding page:
> http://casoilresource.lawr.ucdavis.edu/drupal/node/429
>
> >although i didn't
> > quite get this part:
> > 1. select geometry overlapping the bounding box defined by the current
> > viewport in AEA coordinates, using the PostGIS spatial indexing system
> > 2. compute the intersection between the boinding box and the
> > overlapping polygons
> > 3. compute the centroids of the new geometry
> > 4. convert the polygon geometry to KML
> > 5. convert the centroid geometry to KML
> > 6. return resulting text
>
> This is a list of how the PHP code is functioning; some background--
>
> I have a massive table of polygons, stored in a custom AEA projection.
> Google
> Earth is not happy about massive KML files, so PostGIS is used to
> 'cut-out'
> (intersection) a chunk. This chunk is then converted into KML, with all of
> the extra XML styling etc. added by a PHP wrapper script. A second pass is
> done with PostGIS to get the centroids of the polygons, which are used as
> a
> labeling mechanism. All of the KML / XML chunks are stuck into a
> dynamically
> generated KML document and returned to the user.
>
> I was able to construct this by
> 1. looking over the KML specs
> 2. looking at some example KML files
> 3. experimentation
>
> Further work should definitely use something other than string functions
> to
> build the XML.
>
> Another hint: be sure to send the KML header by PHP first:
>
>                 header("Pragma: public"); // required
>                 header("Expires: 0");
>                 header("Cache-Control: must-revalidate, post-check=0,
> pre-check=0");
>                 header("Content-Type: application/kml; charset=utf8");
>                 header('Content-Disposition: attachment; filename="
> file.kml"') ;
>
>
> check out the examples on the above link, and dissect the resulting KML
> file
> for hints.
>
> Cheers,
>
> Dylan
>
>
>
>
>
> > cheers, jzs
> >
> > On 9/14/07, Jose Gomez-Dans <jgomezdans at gmail.com> wrote:
> > > Hi Maciej,
> > > I sent you an e-mail, but your spam protection system wouldn't allow
> > > the message to go through.  If you have another address, I'll resend
> > > it to you :)
> > >
> > > On 9/14/07, Maciej Skorczewski <maciej.skorczewski at procad.pl> wrote:
> > > > how sql should looks like?
> > >
> > > Simply (and this is already quite advanced: you can use simplify() to
> > > reduce the number of points in your vector data. Ours are very
> > > detailed, and we don't want that on our KML files):
> > >
> > > SELECT AS_KML(SIMPLIFY(the_geom,100)) from MY_TABLE;
> > >
> > > > Question about Python class...i am not python programer can you
> > > > describe my how i can use it?
> > >
> > > You just write a small python program to use it. You should be able to
> > > do the same with PHP.
> > >
> > > Cheers,
> > > José
> >
> > _______________________________________________
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> > postgis-users at postgis.refractions.net
> > http://postgis.refractions.net/mailman/listinfo/postgis-users
>
>
>
> --
> Dylan Beaudette
> Soils and Biogeochemistry Graduate Group
> University of California at Davis
> 530.754.7341
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>
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