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<p class="MsoNormal">I have an area of interest that is split across two UTM zones. My desired end result is a single stitched, clipped, and re-projected image in a local coordinate system.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">My usual workflow is to build a VRT that contain only the input tiles that touch the area of interest. Normally that works great, but not when split across zones. I know it’s possible to create a VRT containing two or more coordinate systems
with the gdalbuildvrt –allow_projection_difference option.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">There are at least two ways I could proceed:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo2"><![if !supportLists]><span style="mso-list:Ignore">A)<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>Two steps: reproject all input tiles to a common base with gdalwarp, then stitch/clip with gdalwarp –t_srs “EPSG:7645” –cutline clip.shp –crop_to_cutline aoi.vrt output.tif (where aoi.vrt contains a list of tiles that touch the AOI)<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo2"><![if !supportLists]><span style="mso-list:Ignore">B)<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>One step: gdalwarp –t_srs “EPSG:7645” mixed_utm_zones.vrt output.tif<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">“B” is nice option in theory. However, in my experiments, it appears that only half the AOI is processed when I try. Option “A” works fine, but it seems like the image would be resampled twice… once for each gdalwarp command?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Can anyone confirm if B is theoretically possible? Better approaches? This must be a common issue.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks for advice!<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">----------------------------------------------<o:p></o:p></p>
<p class="MsoNormal">Jim Lacy <br>
Wisconsin State Cartographer's Office <br>
University of Wisconsin-Madison <br>
(608) 262-6850 <br>
<a href="http://www.sco.wisc.edu/"><span style="color:blue">www.sco.wisc.edu</span></a><o:p></o:p></p>
<p class="MsoNormal">My calendar: <a href="http://go.wisc.edu/xziys4"><span style="color:blue">http://go.wisc.edu/xziys4</span></a><b><span style="color:#333333;background:white"><o:p></o:p></span></b></p>
<p class="MsoNormal"><o:p> </o:p></p>
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