[gdal-dev] Determining GDAL WMS download limit?

[Carl Godkin]

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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