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<p class="MsoNormal"><span lang="EN-US"># Unexpected change in pixel values during processing (Metashape/QGIS)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">## Software<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">* QGIS 3.28<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">* Agisoft Metashape 2.0.1<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">## Description<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I used Agisoft Metashape to create RGB GeoTiff. The source for this GeoTiff are images taken with a UAV (DJI M3M).<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">When loading the GeoTiff into QGIS and processing the file, the pixel values for the same position differ between the original file and the process result.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">My first thought was that I somehow resampled, converted, or transformed the pixel values during the processing.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">So I simplified the process step by step to the bare minimum, but the result stayed the same.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Even just exporting the file leads to changed pixel values.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">## CRS not recognized<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Something I noticed while trying to solve this problem is that QGIS doesn't recognize the GeoTiffs CRS (EPSG:32632) as a predefined CRS but as a custom CRS. This is curious because I use a predefined CRS from Agisoft
Metashape to create the GeoTiff.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I tried to reproject the file and also to just change the CRS in the file's QGIS properties, but the pixel values still differ after processing the file.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">### CRS defined in Agisoft Metashape:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">```<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Projected Coordinate System: WGS 84 / UTM zone 32N (EPSG::32632)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Linear Units: metre (EPSG::9001)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Projection Method: Transverse Mercator<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> Latitude of natural origin: 0<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> Longitude of natural origin: 9<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> Scale factor at natural origin: 0.9996<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> False easting: 500000<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> False northing: 0<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Geographic Coordinate System: WGS 84 (EPSG::4326)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Angular Units: degree (EPSG::9102)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Geodetic Datum: World Geodetic System 1984 ensemble (EPSG::6326)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Ellipsoid: WGS 84 (EPSG::7030)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Prime Meridian: Greenwich (EPSG::8901)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">```<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">### CRS regognized in QGIS:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">```<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">BOUNDCRS[<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> SOURCECRS[<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PROJCRS[<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> "WGS 84 / UTM zone 32N",<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> BASEGEOGCRS[<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> "WGS 84",<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> DATUM[<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> "World Geodetic System 1984",<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ELLIPSOID["WGS 84",6378137,298.257223563,LENGTHUNIT["metre",1]]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PRIMEM["Greenwich",0,ANGLEUNIT["degree",0.0174532925199433]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ID["EPSG",4326]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> CONVERSION[<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> "UTM zone 32N",<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> METHOD["Transverse Mercator",ID["EPSG",9807]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PARAMETER["Latitude of natural origin",0,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8801]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PARAMETER["Longitude of natural origin",9,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8802]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PARAMETER["Scale factor at natural origin",0.9996,SCALEUNIT["unity",1],ID["EPSG",8805]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PARAMETER["False easting",500000,LENGTHUNIT["metre",1],ID["EPSG",8806]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PARAMETER["False northing",0,LENGTHUNIT["metre",1],ID["EPSG",8807]]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> CS[Cartesian,2],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> AXIS["easting",east,ORDER[1],LENGTHUNIT["metre",1]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> AXIS["northing",north,ORDER[2],LENGTHUNIT["metre",1]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ID["EPSG",32632]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> TARGETCRS[<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> GEOGCRS[<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> "WGS 84",<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> DATUM[<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> "World Geodetic System 1984",<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ELLIPSOID["WGS 84",6378137,298.257223563,LENGTHUNIT["metre",1]]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PRIMEM["Greenwich",0,ANGLEUNIT["degree",0.0174532925199433]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> CS[ellipsoidal,2],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> AXIS["geodetic latitude (Lat)",north,ORDER[1],ANGLEUNIT["degree",0.0174532925199433]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> AXIS["geodetic longitude (Lon)",east,ORDER[2],ANGLEUNIT["degree",0.0174532925199433]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ID["EPSG",4326]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ABRIDGEDTRANSFORMATION[<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> "Transformation from WGS 84 to WGS84",<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> METHOD["Position Vector transformation (geog2D domain)",ID["EPSG",9606]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PARAMETER["X-axis translation",0,ID["EPSG",8605]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PARAMETER["Y-axis translation",0,ID["EPSG",8606]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PARAMETER["Z-axis translation",0,ID["EPSG",8607]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PARAMETER["X-axis rotation",0,ID["EPSG",8608]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PARAMETER["Y-axis rotation",0,ID["EPSG",8609]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PARAMETER["Z-axis rotation",0,ID["EPSG",8610]],<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> PARAMETER["Scale difference",1,ID["EPSG",8611]]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">```<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">## Question<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The questions I have are:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">1. What could be the reason for this behavior?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">2. How do I prevent the pixel values from changing?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:DE">Kind regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:DE"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:DE">i.A. Dirk Stulgies<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:DE">**********************************<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:DE"><img width="148" height="31" style="width:1.5416in;height:.3229in" id="Bild_x0020_1" src="cid:image001.png@01D9F773.F2644EA0"></span><span style="mso-ligatures:none;mso-fareast-language:DE"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:DE"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:DE">NPZ Innovation GmbH<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:DE">Hohenlieth-Hof, D-24363 Holtsee<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-ligatures:none;mso-fareast-language:DE">Tel.<span style="color:#1F497D">
</span><a href="tel:%2B49-4351-736%20277" target="_blank">+49-4351-736 277 </a><u><span style="color:#0563C1"><o:p></o:p></span></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-ligatures:none;mso-fareast-language:DE">Fax <span style="color:#1F497D">
</span><a href="tel:%2B49-4351-736%20271" target="_blank"><span style="color:blue">+49-4351-736 271</span></a><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-ligatures:none;mso-fareast-language:DE">Mail:<span style="color:#1F497D">
</span><a href="mailto:d.stulgies@npz-innovation.de" target="_blank">d.stulgies@npz-innovation.de</a><u><span style="color:#0563C1"><o:p></o:p></span></u></span></p>
<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:DE">Web:<span style="color:#1F497D">
</span><a href="http://www.npz-innovation.de/" target="_blank"><span style="color:blue">www.npz-innovation.de</span></a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:DE"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:DE">Firmensitz Hohenlieth, Holtsee
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:DE">Amtsgericht Kiel, HRB 15342 Kl<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:DE">Geschäftsführer: Dr. Gunhild Leckband, Thorsten Pommer<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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