[gdal-dev] WMS Issues two requests?

[Lewis, Martin (UK)]

I need a little help on WMS, it appears to decide that my one request should be two and hence is slowing the whole thing up
I create an XML file and it has the following attributes for DataWindow:

       UpperLeftX                       -10.2210525
       UpperLeftY                        57.7424
       LowerRightX                     4.88191
       LowerRightY                     51.3579
       SizeX                               1076
       SizeY                                787

BlockSize is left at default of 1024 for X and Y

When the request is issued I am noticing in Wireshark TWO requests are sent that appear to have the following BBOX parameters:

Request 1
------------
-10.2210525
49.43529033
4.15203
57.7424

Request 2
------------
4.15203
49.43529033
18.52511
57.7424

So a couple of questions:
1. Why the two requests?
2. Why is the area that ends up in the two requests a lot bigger than the size of the DataWindow that was requested?
3. What am I missing? Is it SizeX being slightly bigger than the block size causing the two fetches? How can it be optimised?

Thanks

Martin

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