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<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">Hi Idan,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">I would like to point out a few issues:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo3"><span lang="EN-GB" style="mso-fareast-language:EN-US">WGS84 is not a projection, therefore it has no projection distortions. The world is an ellipsoid in WGS84, not a rectangular map.
The deformations you refer to is what you get when ones uses the platte-carée projection (x=longitude, y=latitude) as for instance QGIS does by default. Google Earth instead uses a globe for WGS84, so it has (almost) no distortions.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo3"><span lang="EN-GB" style="mso-fareast-language:EN-US">EPSG:4326 is a bad choice for a CRS, as it is 2D and because it is a datum ensemble. It is better specify a specific reference
frame (e.g. WGS84-G1761). Or even better: to use the official international terrestrial reference system (e.g. ITRF2014) in stead of a CRS defined by the military of one random country.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo3"><span lang="EN-GB" style="mso-fareast-language:EN-US">Web Mercator is an approximation mixing spherical formulas and ellipsoidal coordinates. Therefore it is not conformal. True Mercator
is a better choice as it is conformal. I do not believe the more complex computation is a real problem for modern computers.<o:p></o:p></span></li></ul>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">Kind regards, Jochem<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> PROJ <proj-bounces@lists.osgeo.org>
<b>On Behalf Of </b>Idan Miara<br>
<b>Sent:</b> donderdag 26 november 2020 14:47<br>
<b>To:</b> PROJ <proj@lists.osgeo.org><br>
<b>Subject:</b> [PROJ] Why is Web Marcator EPSG:3857 so popular for web maps (vs EPSG:4326)?<o:p></o:p></span></p>
</div>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<div>
<p class="MsoNormal"><span lang="EN-GB">Hi all,<o:p></o:p></span></p>
<div>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-GB">I was wondering if you can enlighten me regarding why Web Marcator (</span><span lang="EN-GB" style="font-size:10.5pt;font-family:"Arial",sans-serif;color:#202122">EPSG:3857) is so popular and used by virtually all major
online map providers as opposed to WGS84 lat/lon (EPSG:4326)?</span><span lang="EN-GB"><o:p></o:p></span></p>
</div>
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<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-GB">I've composed some points that I could think about, but it doesn't add up for why 3857 maps (i.e. slippy map) are more popular than 4326:<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
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<div>
<p class="MsoNormal"><span lang="EN-GB">1. In 3857 almost all the world fits in a rectangular tile (~85 deg north to ~</span><span lang="EN-GB" style="font-size:10.5pt;font-family:"Arial",sans-serif;color:#202122">85 deg south), which makes it easier to divide the
tile further into sub tiles. </span><span lang="EN-GB"><o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.5pt;font-family:"Arial",sans-serif;color:#202122">In 4326 all the world fits into two rectangular tiles (so not much more complicated, I guess).</span><span lang="EN-GB"><o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
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<div>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.5pt;font-family:"Arial",sans-serif;color:#202122">2. Users expect coordinates in 4326 and the transformation from 3857 to 4326 is rather fast (in comparison to ellipsoidal mercator).</span><span lang="EN-GB"><o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-GB">But if you save the coordinates in 4326 then you wouldn't need to transform at all.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-GB">3. 3857 is "almost" conformal - I think that the normal use case is not marine navigation so it doesn't seem so important.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-GB">4. Both 3857 and 4326 have size distortion.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-GB">5. You can't measure distances, areas or angles easier in 3857 as far as I know.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-GB">What am I missing? Is 3857 faster or more useful in any other way than 4326?<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal">Kind regards,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Idan<o:p></o:p></p>
</div>
</div>
</div>
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