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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">I used the gdal_compare script
<a href="https://gdal.org/programs/gdalcompare.html">https://gdal.org/programs/gdalcompare.html</a>
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><br>
gdalcompare st4_pr.2017092016.01h st4_pr.2017092016.01h.tif<br>
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<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">and it reports three differences:<o:p></o:p></span></p>
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<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1"><span lang="EN-US" style="mso-fareast-language:EN-US">Files differ at the binary level (normal, GRIB and tif are not the same)<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1"><span lang="EN-US" style="mso-fareast-language:EN-US">Difference in SRS (but they are alike, * IsSame() reports them as equivalent.)<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1"><span lang="EN-US" style="mso-fareast-language:EN-US">Difference in Dataset metadata key count ( ['AREA_OR_POINT'] added)<br>
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<o:p></o:p></span></li></ul>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">So if I read the report right the pixels in the files are identical. All I can conclude is that gdal_compare and your R script are doing something in different ways.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">-Jukka Rahkonen-<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b>Lähettäjä:</b> gdal-dev <gdal-dev-bounces@lists.osgeo.org>
<b>Puolesta </b>Furuya, Takahiro via gdal-dev<br>
<b>Lähetetty:</b> torstai 1. helmikuuta 2024 1.53<br>
<b>Vastaanottaja:</b> gdal-dev@lists.osgeo.org<br>
<b>Aihe:</b> [gdal-dev] gdal_translate shifted values<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hi gdal-dev, I am Takahiro, a student who is using gdal_translate.
<o:p></o:p></p>
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<p class="MsoNormal">I have an issue with gdal_translate and would like to ask a question.<o:p></o:p></p>
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<p class="MsoNormal">I used gdal_translate to transform a NCEP GRIB file (downloadable from <a href="https://data.eol.ucar.edu/cgi-bin/codiac/fgr_form/id=21.093">https://data.eol.ucar.edu/cgi-bin/codiac/fgr_form/id=21.093</a>, or attached to this email) to
GeoTiff, and compare those 2 data formats. The command I used is<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:8.5pt;font-family:"Menlo",serif">>gdal_translate -of GTiff st4_pr.2017092016.01h st4_pr.2017092016.01h.tif<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">(The GRIB file I used was st4_pr.2017092016.01h, which can be downloaded from the above link by specifying “Begin Date/Time” to “20170920”/“15:00:00” and “End Date/Time” to “20170920”/“15:59:59”.)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Then I read the 2 data files in R and checked if the original value at a certain grid cell in the GRIB file remained at the same grid cell in the GeoTiff file, but the value was shifted by 6 rows (the value I checked was 9.75 [mm/hour]
that was stored in index [100,86] in the original GRIB file, but it was shifted to [106,86] in the GeoTiff file).<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">You can see the Python script used for reading the original GRIB file here: <a href="https://bpa.st/ZNOSI">https://bpa.st/ZNOSI</a><o:p></o:p></p>
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<p class="MsoNormal">The R script used for checking the tif-translated data: <a href="https://bpa.st/WZLSY">https://bpa.st/WZLSY</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">The version of gdal_translate I used is 3.0.2.<o:p></o:p></p>
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<p class="MsoNormal">Is this a known issue of gdal_translate? Or is this issue not supposed to happen (is this the mistake of my side?)?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Best regards,<o:p></o:p></p>
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<p class="MsoNormal">Takahiro<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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