Arne,
Thanks for your reply. It sounds like layer groups may be what I
need. I have tested the Image mosaic plugin and it does work and it
is very similar to setting up tileindexed layers in mapserver.
Like geoserver mapserver does do image resampling, however we try to
increase the performance by preprocessing the source imagery to lower
resolutions so that when mapserver is processing a request at a small
scale (1:5000000) it doesn't have to read and resample the thousands
of full resolution source tiffs.
Typically we do something like this in the mapserver mapfile:
# tiles are 10km x 10km
LAYER
NAME "ny_low_res"
TILEINDEX 10m_resolution/newyork_10km_tindex.shp
TYPE RASTER
GROUP "ny_ortho"
CLASS
MAXSCALE 10000000
MINSCALE 50000
END
END
# tiles are 5km x 5km
LAYER
NAME "ny_medium_res"
TILEINDEX 2m_resolution/newyork_5km_tindex.shp
TYPE RASTER
GROUP "ny_ortho"
CLASS
MAXSCALE 50000
MINSCALE 7500
END
END
# tiles are 1km x 1km
LAYER
NAME "ny_high_res"
TILEINDEX 30cm_resolution/newyork_1km_tindex.shp
TYPE RASTER
GROUP "ny_ortho"
CLASS
MAXSCALE 7500
END
END
In the tile cache configuration file or in a wms I can request
LAYERS=ny_ortho. I do something simalar for boundaries - country /
state / county.
Thanks
2009/3/26 Arne Kepp <ak@anonymised.com>:
Hi Travis,
not sure I follow completely, but I'll try to explain and you can ask more
specifically if there are gaps:
GeoWebCache does not merge layers at this point. But in GeoServer you can
define "layer groups", which is a collection of layers in a specific order.
I think this is the equivalent to the grouping? GeoServer does all the
raster reading, processing, subsampling, merging etc.
WMS servers, like GeoServer, generally dont operate on fixed scales. You can
ask for any scale and it'll downsample as necessary. On the other hand,
GeoWebCache makes tiles for specific resolutions, meaning min-, maxscale and
every step in between. Those are configurable.
Whether you can use your source data directly depends on what kind of format
it is in? What you describe sounds similar to ImageMosaics:
http://geoserver.org/display/GEOSDOC/Using+the+ImageMosaic+plugin
Hope this helps,
-Arne
Travis Kirstine wrote:
I have some general questions regarding the display of rasters using
geoserver compared to mapserver. We currently have a fairly large
archive of high resolution orthophoto and currently are severing it to
a google maps based client using mapserver with tilecache. We have
put a lot of work into structuring our source data specifically for
mapserver, we downsample the high resolution images to mid and low
resolution images then merge the images to larger tiles based on
resolution and build overviews. We are then able to configure the
mapserver mapfile to GROUP the layers together and have mapserv /
tilecache access the proper resolution based on zoom level by setting
the MINSCALE / MAXSCALE for each layer.
With geoserver are you able to control the min / max scales at which
layers can be drawn? Are you able to request a "group" or multiple
coverages / feature types (geoserver gwc merges the layers)?
Thank for the insight
--
Arne Kepp
OpenGeo - http://opengeo.org
Expert service straight from the developers
--
Travis K.
Toronto, Canada
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and that failure's no success at all."
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