Hi,<br><br>I'm not sure about this problem, I suspect cascading the vrt datasets should normally work. Could you provide your complete C# example to produce the output and the gdal_warp command line to examine the difference? <br>
<br>Best regards,<br><br>Tamas<br><br><br><br><div class="gmail_quote">2009/5/31 edomazlicky <span dir="ltr"><<a href="mailto:edomazlicky@gmail.com">edomazlicky@gmail.com</a>></span><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>
I am trying to warp a NAD27 UTM file to Google Mercator 900913. My<br>
understanding is that for this to happen you have to first warp the file to<br>
WGS84 and then to 900913. I have tried going straight from NAD27->900913 and<br>
I get projection errors similar to if you plotted a WGS84 coordinate on a<br>
NAD27 map. So to accomplish this two-step warp I have been trying to do<br>
something kind of like this:<br>
<br>
Dim oWGS84 As New OSGeo.OSR.SpatialReference("")<br>
' WGS84 UTM Zone 10<br>
oWGS84.ImportFromEPSG(32610)<br>
Dim wgs84_wkt As String = ""<br>
oWGS84.ExportToPrettyWkt(wgs84_wkt, 0)<br>
InterMed = OSGeo.GDAL.Gdal.AutoCreateWarpedVRT(SrcGdalDataSet, src_wkt,<br>
wgs84_wkt, eReSample, 0.125)<br>
GdalDataSet = OSGeo.GDAL.Gdal.AutoCreateWarpedVRT(InterMed, wgs84_wkt,<br>
dst_wkt, eReSample, 0.125)<br>
<br>
Where src_wkt contains the NAD27 WKT and dst_wkt contains the 900913 WKT.<br>
This doesn't work- I am getting the same results I get if I try to go<br>
straight from NAD27->900913. However if instead I warp the file in gdal_warp<br>
first to WGS84 and then go from that to 900913 it works fine. Is there<br>
anyway to warp these files without making a new file fist? I would like for<br>
it all to be done in memory without messing with temporary files or calling<br>
gdal_warp externally.<br>
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