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Process is very simple</div>
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<li><span><span style="text-align: start; background-color: rgb(24, 26, 27); --darkreader-inline-bgcolor:#131516; display: inline !important;" data-darkreader-inline-bgcolor="">Take our tiles and build a virtual raster: <br>
</span><span style="text-align: start; background-color: rgb(24, 26, 27); --darkreader-inline-bgcolor:#131516; display: inline !important;" data-darkreader-inline-bgcolor="">gdalbuildvrt -r lanczos -resolution HIGHEST output.vrt -input_file_list input_file_list.txt</span><br>
</span></li><li><span><span style="text-align: start; background-color: rgb(24, 26, 27); --darkreader-inline-bgcolor:#131516; display: inline !important;" data-darkreader-inline-bgcolor="">Convert our virtual raster to a GeoTIFF:</span></span></li><li style="display: block;"><span><span style="text-align: start; background-color: rgb(24, 26, 27); --darkreader-inline-bgcolor:#131516; display: inline !important;" data-darkreader-inline-bgcolor="">gdal_translate -of GTIFF ./output.vrt ./output.tif</span><br>
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<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; background-color: rgb(255, 255, 255); --darkreader-inline-color:#e8e6e3; --darkreader-inline-bgcolor:#181a1b;" data-darkreader-inline-color="" data-darkreader-inline-bgcolor="">The
artifacts occur with all resolution methods (nearest, bilinear, cubic, cubicspline, lanczos, average, mode) to varying degrees.</span><br>
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<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; background-color: rgb(255, 255, 255); --darkreader-inline-color:#e8e6e3; --darkreader-inline-bgcolor:#181a1b;" data-darkreader-inline-color="" data-darkreader-inline-bgcolor=""><br>
</span></div>
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It appears to worsen when more and more tiles overlay a location and when more scaling is needed.</div>
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I can provide a sample case that reproduces this:<br>
<br>
Public Drive Link to archive: <a href="https://drive.google.com/file/d/1Tu4_A5NLiG0CQytuIQeeqr6JOVdAZDqu/view?usp=sharing" id="LPlnk194316">https://drive.google.com/file/d/1Tu4_A5NLiG0CQytuIQeeqr6JOVdAZDqu/view?usp=sharing</a><br>
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Archive contains 6 files:<br>
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img_1.tif - A low resolution (1m) GTIFF image to be rendered behind the second image.<br>
img_2.tif - A high resolution (0.3m) GTIFF image to be rendered above the first image.<br>
<span style="background-color: rgb(255, 255, 255); display: inline !important; --darkreader-inline-bgcolor:#181a1b;" data-darkreader-inline-bgcolor="">output.vrt - The VRT we generated using the above command from Step 1.</span><br>
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our_output.tif - The GTIFF mosaic generated using the above gdal_translate command from Step 2.</div>
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blue_dots_in_our_output.png - A zoomed in screenshot of some of the blue dots in the sample (the blue dots in this sample are unfortunately minor compared to what we have seen in our un-shareable data)<br>
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more_blue_dots_from_other_samples.png - A screenshot of some of the blue/yellow dots we see in some of our other samples which we cannot share.<br>
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Other relevant information:<br>
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<ul>
<li><span>Attempted on GDAL 3.0.4, GDAL 3.2.1, and GDAL 3.2.3</span></li></ul>
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<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; background-color: rgb(255, 255, 255); --darkreader-inline-color:#e8e6e3; --darkreader-inline-bgcolor:#181a1b;" data-darkreader-inline-color="" data-darkreader-inline-bgcolor="">Any
help would b</span><span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; background-color: rgb(255, 255, 255); --darkreader-inline-color:#e8e6e3; --darkreader-inline-bgcolor:#181a1b;" data-darkreader-inline-color="" data-darkreader-inline-bgcolor="">e greatly
appreciated,</span><br>
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Raymond</div>
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