<div dir="ltr">Even,<div><br></div><div>Thanks for your reply. I get it now. :)</div><div><br></div><div>I am new to gdal in general. For context, why does CreateCopy() choose the nearest zoom level and not SetGeoTransform()? As a new user, it seems to me the ZOOM_LEVEL_STRATEGY should apply to both the SetGeoTransform() and CreateCopy().</div><div><br></div><div>Thanks again,</div><div>Roarke</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Sep 13, 2017 at 3:50 PM, Even Rouault <span dir="ltr"><<a href="mailto:even.rouault@spatialys.com" target="_blank">even.rouault@spatialys.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><u></u>
<div style="font-family:'monospace';font-size:9pt;font-weight:400;font-style:normal">
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">On mercredi 13 septembre 2017 15:38:55 CEST Roarke Gaskill wrote:</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> Hi,</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> </p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> In the GDALGeoPackageDataset</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> <<a href="https://github.com/OSGeo/gdal/blob/65dea1c999b6b5f692c945ea074b04cb5e43eca4" target="_blank">https://github.com/OSGeo/<wbr>gdal/blob/<wbr>65dea1c999b6b5f692c945ea074b04<wbr>cb5e43eca4</a></p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> /gdal/ogr/ogrsf_frmts/gpkg/<wbr>ogrgeopackagedatasource.cpp#<wbr>L1819> class it</p><span class="">
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> appears the zoom level in the SetGeoTransform function does not calculate</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> the zoom level correctly. Also, it is different from the zoom level</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> calculation in CreateCopy</p>
</span><p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> <<a href="https://github.com/OSGeo/gdal/blob/65dea1c999b6b5f692c945ea074b04cb5e43eca4" target="_blank">https://github.com/OSGeo/<wbr>gdal/blob/<wbr>65dea1c999b6b5f692c945ea074b04<wbr>cb5e43eca4</a></p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> /gdal/ogr/ogrsf_frmts/gpkg/<wbr>ogrgeopackagedatasource.cpp#<wbr>L4079> function. The</p><span class="">
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> zoom level calculation in the CreateCopy appears to work as I would expect.</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> </p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> The transform I am using to test is:</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> [-20037508.342789248, 6176.637812966647, 0.0, 19971868.880408563, 0.0,</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> -6177.590116052211]</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> </p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> The CreateCopy zoom level logic produces level 5. Which is what I would</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> expect.</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> </p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> The SetGeoTransform zoom level logic is not able to identify a zoom level.</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> </p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">> Is the SetGeoTransform zoom level calculation logic wrong?</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"> </p>
</span><p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">Roarke,</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"> </p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">when using SetGeoTransform() and a pre-defined tiling scheme (here I assume you must use GoogleMapsCompatible), the resolution of the geotransform matrix passed to SetGeoTransform() must exactly match the base resolution of the tiling scheme divided by a power of 2</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"> </p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">>>> 156543.0339280410 / 6176.637812966647</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">25.344376450147266</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"> </p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">which is not a power of 2.</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"> </p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">CreateCopy() in the GPKG implementation with a pre-defined tiling scheme identifies the closest zoom level for your source dataset and then resample it so its resolution matches exactly one of the zoom levels.</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"> </p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">Even</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"> </p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">-- </p>
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