Hi Frank,<br><br>I've theorized all sorts of reasons for what I'm seeing. So far none of them are right. Basically, if I take a really high-res epsg:4326 image, and serve it up through Mapserver in epsg:900913, there are instances where I get images back which are missing rows of pixels at the bottom of the image. If I reduce the resolution of the image the lines go away. I haven't yet figured out at what resolution the problem starts to appear.<br>
<br>I just tested the idea of changing the values in the warper code:<br>First:<br>nResWinSize += 100;<br>
Then:<br>nResWinSize += 500;<br>
<br>Then rebuilt gdal. Didn't seem to make a difference.<br><br>Thanks for the info though.<br><br>Roger<br>--<br><br><div class="gmail_quote">On Tue, Nov 18, 2008 at 5:07 PM, 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 class="Ih2E3d">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;">
I've been mercilessly beating a dead horse on a couple of lists about some weird artifacts that I'm getting when doing reprojections in Mapserver from epsg:4326 to epsg:900913. It's recently come to my attention that something was discussed in an IRC chat that might be pertinent to this issue, and I was hoping I could test it. Specifically, it relates to SOURCE_EXTRA, and although the conversation at the time dealt with issues at the International dateline, I think it might also manifest itself in other edge cases (literal edges). ;).<br>
<br>
I would like to know if it is possible to set SOURCE_EXTRA to something other than 1 at compile time? I do not see it listed as an option in the configure documentation, but perhaps I could edit a file, or pass in the flag anyhow?<br>
</blockquote>
<br></div>
Roger,<br>
<br>
I haven't followed your problems closely (I recall something about datum<br>
shifts). The SOURCE_EXTRA only helps with the GDAL warper. If you wanted<br>
you could modify the following code in gdal/alg/gdalwarpoperation.cpp<br>
and recompile:<br>
<br>
/* -------------------------------------------------------------------- */<br>
/* Allow addition of extra sample pixels to source window to */<br>
/* avoid missing pixels due to sampling error. In fact, */<br>
/* fallback to adding a bit to the window if any points failed */<br>
/* to transform. */<br>
/* -------------------------------------------------------------------- */<br>
if( CSLFetchNameValue( psOptions->papszWarpOptions,<br>
"SOURCE_EXTRA" ) != NULL )<br>
{<br>
nResWinSize += atoi(<br>
CSLFetchNameValue( psOptions->papszWarpOptions, "SOURCE_EXTRA" ));<br>
}<br>
else if( nFailedCount > 0 )<br>
nResWinSize += 10;<br>
<br>
<br>
Perhaps change the nResWinSize += 10 line to nResWinSize += 100 or something<br>
like that.<br>
<br>
Best regards,<br><font color="#888888">
-- <br>
---------------------------------------+--------------------------------------<br>
I set the clouds in motion - turn up | Frank Warmerdam, <a href="mailto:warmerdam@pobox.com" target="_blank">warmerdam@pobox.com</a><br>
light and sound - activate the windows | <a href="http://pobox.com/%7Ewarmerdam" target="_blank">http://pobox.com/~warmerdam</a><br>
and watch the world go round - Rush | Geospatial Programmer for Rent<br>
<br>
</font></blockquote></div><br>