[gdal-dev] WMS Issues Two Requests

Martin Lewis MLewis at ngms.eu.com
Fri Feb 7 06:08:07 PST 2014


Thanks Jukka.

I have been having a play around and the 'width' and 'height' sent in the
WMS Request string appears to be BlockSizeX and BlockSizeY and I think I
understand now.

Removing the BlockSizeX and Y  from the XML meant that block size was
defaulted to 1024 and 1024 - again resulting in two requests.

Setting BlockSize to 256 and 256 and you get loads of requests as expected
to fulfil the whole request of 1076 * 787

However setting the BlockSizeX and Y to the same as SizeX and SizeY (1076,
787) in the DataWindow section, created a WMS Request that had 'height' and
'width' set to 787 and 1076 - which appears to be exactly what is required.

This cut the time from start of request to drawing on the screen by 5 times
- from 5 secs to 1 sec, exactly what I was after.

I suppose some WMS servers may not support the BlockSize that is being
requested. (when I set the BlockSize to 2048, one map server was returning
an error saying it was above the allowed 2001 width!!?)

However at the current moment what is requested appears to be within limits
of all the servers we talk to.

Is it as simple as this or is there anything that I have missed?

Once again thanks for your help.

Martin



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