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<p>Greetings, <br>
</p>
<p>I received an email from two users with 3.12 asking about
"Ballpark Transformations" - the exact phrase was "Used a Ballpark
transformation from EPSG:4326 to EPSG: 2274". <br>
</p>
<p>I've been able to generate the message twice by: <br>
</p>
<ul>
<li>changing the projection of a new project with no data from
4326 to 2274 <br>
</li>
<li>adding data with an incorrect spatial extent that I believe
was in 4326 and applied to a project in 2274 (I think - I
currently don't have access to that data to confirm)<br>
</li>
</ul>
<p>I've found mention of it here:
<a class="moz-txt-link-freetext"
href="https://qgis.org/api/classQgsCoordinateTransform.html#a16adb051fafc25058c0040a310f1606b">https://qgis.org/api/classQgsCoordinateTransform.html#a16adb051fafc25058c0040a310f1606b
</a><br>
</p>
<p>The expanded message in QGIS is: <br>
</p>
<p><span>
<div class="Qynugf">
<p style=" margin-top:12px; margin-bottom:12px;
margin-left:0px; margin-right:0px; -qt-block-indent:0;
text-indent:0px;"><i><b>An alternative, ballpark-only
transform was used when transforming coordinates between
</b></i><i><b>EPSG:4326 - WGS 84</b></i><i><b> and </b></i><i><b>EPSG:2274
- NAD83 / Tennessee (ftUS)</b></i><i><b>. The results
may not match those obtained by using the preferred
operation:</b></i><i><b>
</b></i></p>
<p style=" margin-top:12px; margin-bottom:12px;
margin-left:0px; margin-right:0px; -qt-block-indent:0;
text-indent:0px;"><i><b>Possibly an incorrect choice of
operation was made for transformations between these
reference systems. Check the Project Properties and
ensure that the selected transform operations are
applicable over the whole extent of the current project.</b></i></p>
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</span>If I check the project properties there is no Datum
Transformation defined after all this happens. <br>
<span></span></p>
<p>I'm assuming that if a project has no data and one jumps datums
by changing the projection it's saying "Hey since there is no data
this transformation is a "ballpark" i.e. not exact". Is there a
preferred way to dealing with this after it happens? <br>
</p>
<p>Randy<br>
</p>
<pre class="moz-signature" cols="72">--
Randal Hale
<a class="moz-txt-link-abbreviated" href="mailto:rjhale@northrivergeographic.com">rjhale@northrivergeographic.com</a>
(p) 423.653.3611
<a class="moz-txt-link-freetext" href="http://www.northrivergeographic.com">http://www.northrivergeographic.com</a></pre>
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