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<p>Hi Dirk,</p>
<p>there is no such thing as "<span lang="EN-US">just exporting".
What exactly do you do? What does gdalinfo say about the
original file and the exported file?</span></p>
<p><span lang="EN-US">Cheers, Hannes<br>
</span></p>
<div class="moz-cite-prefix">Am 05.10.23 um 10:10 schrieb Stulgies
Dirk via QGIS-User:<br>
</div>
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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
style="width:1.5416in;height:.3229in" id="Bild_x0020_1"
src="cid:part1.h5872KF8.uWpUctDk@wheregroup.com" class=""
width="148" height="31"></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
style="mso-ligatures:none;mso-fareast-language:DE"
lang="EN-US">Tel.<span style="color:#1F497D">
</span><a href="tel:%2B49-4351-736%20277" target="_blank"
moz-do-not-send="true">+49-4351-736 277 </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"
lang="EN-US">Fax <span style="color:#1F497D">
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moz-do-not-send="true"><span style="color:blue">+49-4351-736
271</span></a><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="mso-ligatures:none;mso-fareast-language:DE"
lang="EN-US">Mail:<span style="color:#1F497D">
</span><a href="mailto:d.stulgies@npz-innovation.de"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">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" moz-do-not-send="true"><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
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<p class="MsoNormal"><span
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<p class="MsoNormal"><o:p> </o:p></p>
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