Hi Frank,<br><br>Thanks for the reply. It might be worth keeping the option to control layer ordering somehow in a mosaic. The reason I'm exploring this is to see if it's possible to emulate the ArcGIS 10 "closest to center" behavior. I'm thinking that if I dynamically write the VRT, I can control how images are overlapped in response to the BBOX extents specified in a WMS request.<br>
<br>Roger<br>--<br><br><div class="gmail_quote">On Tue, Jun 22, 2010 at 8:16 AM, Frank Warmerdam <span dir="ltr"><<a href="mailto:warmerdam@pobox.com">warmerdam@pobox.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div><div></div><div class="h5">Roger André wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Hi All,<br>
<br>
I'd like to control the order in which overlapping images are displayed in a mosaic. Is it possible to do that by using a VRT, and altering the order in which the files are defined in it?<br>
<br>
The online doc for gdalbuildvrt states, "If there is some amount of spatial overlapping between files, the order may depend on the order they are inserted in the VRT file, but this behaviour should not be relied on."<br>
<br>
Not sure if this disclaimer is for the gdalbuildvrt utility, or describes the generic behavior of a raster VRT.<br>
</blockquote>
<br></div></div>
Roger,<br>
<br>
I believe the statement applies to the VRT format itself. I have looked<br>
at the code, and it always applies them linearly based on the order they<br>
appear in the .VRT list of sources. I think you could depend on it "for now"<br>
though in a future version we might do something more fancy that would<br>
result in alternate ordering.<br>
<br>
Best regards,<br><font color="#888888">
-- <br>
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I set the clouds in motion - turn up | Frank Warmerdam, <a href="mailto:warmerdam@pobox.com" target="_blank">warmerdam@pobox.com</a><br>
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<br>
</font></blockquote></div><br>