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<div class="moz-cite-prefix">Le 19/07/2022 à 17:02, Oleg Bizin a
écrit :<br>
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<blockquote type="cite"
cite="mid:CADWt3QQmRytQWUsNTmoJqeBYojSSnY5LAbHPomArPT97N_x9Kg@mail.gmail.com">
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<div dir="ltr">Even,
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<div>Thank you for the detailed answer!<br>
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<div>I have a couple more clarifying questions.<br>
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<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">More
generally PROJ >= 6 will not use WGS 84 as a compulsory
pivot in coordinate transformations</blockquote>
<div>1. Is it correct that the PROJ < 6 definitely uses
WGS84 as a compulsory pivot?</div>
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</blockquote>
When there was a datum indication in the PROJ.4 string, yes, since
+towgs84 or +nadgrids implied the WGS84 pivot. When source and
transformation CRS PROJ.4 strings used the same +towgs84 terms, that
was skipped as an optimization (what newer PROJ does too)<br>
<blockquote type="cite"
cite="mid:CADWt3QQmRytQWUsNTmoJqeBYojSSnY5LAbHPomArPT97N_x9Kg@mail.gmail.com">
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<div>2. Currently, before your fix, for custom crs
transformation to WGS84 may perform, but without significant
impact on accuracy?</div>
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<p>For most uses yes, it shouldn't have significant impact. Unless
you transformation coordinates back and forth many many times.<br>
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<pre class="moz-signature" cols="72">--
<a class="moz-txt-link-freetext" href="http://www.spatialys.com">http://www.spatialys.com</a>
My software is free, but my time generally not.</pre>
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