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I'm new to this mailing list. I couldn't find a way to search the
list archives, so forgive me if this is a duplicate.<br>
<br>
The "Meters at Scale" sizing option looks like a nice addition in
QGIS 3. I would like to use it as a CRS-independent alternative to
"map units".<br>
<br>
I don't find "Meters at Scale" documented, but what I think it <i>should</i>
do is set a size in actual meters (on the earth), independent of
latitude and independent of CRS.<br>
<br>
But that's not what's happening. To duplicate what I'm looking at:<br>
<ol>
<li>Create a new QGIS project.</li>
<li>Set the project CRS to WGS 84, EPSG:4326.</li>
<li>Make a new temporary scratch layer with MultiLineString /
MultiCurve geometry, with CRS of EPSG:4326 - WGS 84.</li>
<li>Add a horizontal line feature near 48 degrees north latitude.
Style the line as "Simple line" with a "Stroke width" of 100
"Meters at Scale".</li>
<li>Zoom in on the line and measure its width with the Measure
tool. It measures around 149.5 meters. Shouldn't it be 100
meters wide? The 149.5 meters width seems to be 100/cos(48°).</li>
<li>Now, just for fun, change the project CRS to WGS 84 / Pseudo
Mercator, EPSG:3857. When you hit "Apply", the line snaps to a
smaller width, which measures as 66.8 meters. It went from too
large to too small. The 66.8 meters width seems to be
100*cos(48°) -- now multiplied by the cosine rather than
divided. I don't know where that's coming from.</li>
</ol>
<p>If I follow the above steps, but draw the line at the equator
instead at 48 degrees north latitude, its width measures 100
meters, with either project CRS.</p>
<p>I also tried it with point geometry, styled with a Simple marker
-- a square sized at 100 "Meters at Scale". Same result.<br>
</p>
<p>So it seems like "Meters at Scale" isn't working right. For one
thing, I think its sizing should be independent of the project
CRS. I'm hesitant to start using it in my QGIS projects, for fear
that this is a bug and when it is fixed, my maps will suddenly
change, and I'll have to go back through them and fix the styles.<br>
</p>
Regards,<br>
--Mark<br>
<br>
<div class="moz-signature">-- <br>
Mark Newbold
<br>
Port Angeles, Washington, USA
<font color="010101"> </font>
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