Is there any way to check for this or protect against it from the
client side, or do you just have to be experienced with a given WMS
service?
Not much to do on the client side, except checking that if you got a
all-white image, it is probably not what you want, and retry at a
coarser resolution. I guess such a logic could potentially be
implemented in the WMS driver, but it could cause confusion to end
users (the driver would have to upsample the downsampled request, and so
the user might not realize that they didn't get data at the resolution
they requested)
Thanks again,
carl
On Sat, Aug 21, 2021 at 12:33 AM Even Rouault
<[email protected] <mailto:[email protected]>> wrote:
Nothing wrong from your side, but the second command probably
selects a higher zoom level that has blank data given the
configuration/data available on the server side.
Le 21/08/2021 à 03:36, Carl Godkin a écrit :
Hi,
I'm very puzzled about why gdal_translate (v. 3.3.1) returns an
all-white image when I select a smaller area than with a working
case with a larger area.
These two command lines are exactly the same except that the
failing case has a smaller area:
gdal_translate
"https://basemap.nationalmap.gov:443/arcgis/services/USGSImageryTopo/MapServer/WmsServer?SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&LAYERS=0&SRS=EPSG:4326&BBOX=-179.999989,-89.000000,179.999988,89.000000
<https://basemap.nationalmap.gov:443/arcgis/services/USGSImageryTopo/MapServer/WmsServer?SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&LAYERS=0&SRS=EPSG:4326&BBOX=-179.999989,-89.000000,179.999988,89.000000>"
wms.xml -of WMS
gdal_translate \
-projwin 524136.39 5229915.17 527111.89 5226499.96 \
-projwin_srs EPSG:32610 \
-outsize 2500 0 \
wms.xml fails.tif
gdal_translate \
-projwin 517947.80 5235658.96 528189.82 5224344.74 \
-projwin_srs EPSG:32610 \
-outsize 2500 0 \
wms.xml works.tif
Can anyone explain what's going on here and (most likely!) what
I'm doing wrong?
Thank you very much,
carl
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