[gdal-dev] Determining GDAL WMS download limit?

[Andre Vautour]

Looks like that server only has 7 levels for that satellite layer:
http://mt.google.com/vt/lyrs=s&x=0&y=0&z=7
http://mt.google.com/vt/lyrs=s&x=0&y=0&z=8

The terrain and map layers have 22 levels:
http://mt.google.com/vt/lyrs=t&x=0&y=0&z=22
http://mt.google.com/vt/lyrs=t&x=0&y=0&z=23
http://mt.google.com/vt/lyrs=m&x=0&y=0&z=22
http://mt.google.com/vt/lyrs=m&x=0&y=0&z=23

So, you'd have to change the TileLevel element:
<TileLevel>7</TileLevel>

That smaller size probably ended up querying tile levels < 8 which is 
why it worked.
André


On 2015-07-07 11:02, Carl Godkin wrote:
>
> Hi,
>
> I would like to know if there's a way to determine if a GDAL WMS download
> is going to work or not from the information in the local description 
> file.
>
> I'm using C++ code to do this, but can illustrate my question with a 
> gdal_translate
> command.  This command fails:
>
> gdal_translate -outsize 6700 6700 \
>      -srcwin 144884562 100729336 178000 178687 \
>      frmt_wms_googlemaps_tms.xml \
>      out.tif
>
> Input file size is 268435456, 268435456
> 0...10...20...30...40...50...60...70ERROR 1: GDALWMS: Unable to 
> download block 35372, 24624.
>   URL: http://mt.google.com/vt/lyrs=s&x=35372&y=24624&z=16
>   HTTP status code: 404, error: (null).
> ERROR 1: frmt_wms_googlemaps_tms.xml, band 1: IReadBlock failed at X 
> offset 35372, Y offset 24624
>
> but if I change the -outsize arguments to 6500 and 6500, it works fine.
>
> I am perfectly willing to accept the limitations of what's available, 
> but can I tell where that limit will be?
>
> The service file is from the frmts/wms directory with the "Satellite" 
> ServerURL line active instead of the "Map" line.
>
> Notes:
> 1. Curiously, the default "Map" ServerURL works to much higher 
> resolution (at least 15000) which makes me
> think that the answer to my question will be "no" since the service 
> description files are otherwise identical!
> 2. The map area above is Italy, but I see the same sort of behavior 
> around the world.
>
> I am using GDAL 1.11.2 on Windows7 x64, but see the same behavior on 
> Linux RHEL5 64-bit as well.
>
> Thank you very much for any insight,
>
> carl
>
>
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