Hi,
I published WCS service providing over 60 000 orthoimagery GeoTIFFs with a
pixel size of 0.25 m or smaller. I am using MapServer 7.2.2 on Debian 10 stable
with Postgis 12. The good thing is that the service works.
However, in the typical use case scenario I want to connect and use the service
in QGIS and this is where the problem starts. QGIS 3.10.11 after connecting to
the service sends GetCoverage request with BBOX covering the full spatial
extent of all connected orthoimagery sheets. MapServer tries to create an
overview image out of over 60 000 individual images and eventually fails for
obvious reasons. QGIS also freezes for around 60 seconds till the service
timeout is reached.
I tried to apply MAXSCALEDENOM, MAXGEOWIDTH and SCALETOKEN parameters to a map
file to allow the user to download the data only starting from particular a
rather large scale, but the parameters are not recognized by WCS (yet they work
for WMS). Currently, as a workaround, I use MAXFEATURES parameter set to 10,
yet it is not a nice solution because, in case of request covering large areas,
it leads to image output with a bunch of empty spaces.
Is there any other way to limit the area for which WCS service sends a proper
response (similarly to MAXSCALEDENOM in case of WMS service)?
This is part of my current, working map file.
LAYER
NAME "Index_orthoimagery"
STATUS OFF
#MAXGEOWIDTH 0.001
MAXFEATURES 10
CONNECTIONTYPE POSTGIS
CONNECTION "host=localhost dbname=postgis user=login password=pass
port=5432"
DATA "geom FROM (SELECT * FROM orto WHERE colour <> 'CIR' ORDER BY date
ASC) AS subquery USING UNIQUE id USING SRID=2180"
PROJECTION
"init=epsg:2180"
END
TYPE POLYGON
PROCESSING "CLOSE_CONNECTION=DEFER"
#MAXSCALEDENOM 12099
END
LAYER
NAME "Orthoimagery"
STATUS OFF
UNITS Meters
TILEINDEX "Index_orthoimagery"
TILEITEM "url_zfs"
METADATA
"wcs_label" "Orthoimagery"
"wcs_rangeset_name" "RGB"
"wcs_rangeset_label" "Red Grean Blue"
"ows_srs" "EPSG:2180"
"wcs_extent" "160828.34326572 98928.8977745594 876029.97009323
796521.669409553"
"wcs_resolution" "0.1 0.1"
"wcs_bandcount" "3"
"wcs_band_names" "R G B"
"wcs_formats" "GEOTIFF"
"wcs_nativeformat" "24-bit GeoTIF"
"wcs_enable_request" "*"
END
TYPE RASTER
PROJECTION
"init=epsg:2180"
END
END
Best regards,
Marcin
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