<p dir="ltr">Hi,</p>
<p dir="ltr">The easiest way for now is to simply save the layer in the other CRS ( "save as" and reproject the file) so that both have the same CRS. Then, you don't need to use OTF.</p>
<p dir="ltr">Ultimately, a fix for OTF would be best but I believe, complicated from what I have read as this relies, If I understand correctly, on libraries external to QGIS.<br></p>
<p dir="ltr">Nicolas </p>
<div class="gmail_extra"><br><div class="gmail_quote">On Jul 18, 2016 00:58, "Brent Wood-2 [via OSGeo.org]" <<a href="/user/SendEmail.jtp?type=node&node=5276901&i=0" target="_top" rel="nofollow" link="external">[hidden email]</a>> wrote:<br type="attribution"><blockquote style='border-left:2px solid #CCCCCC;padding:0 1em' class="quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div style="color:#000;background-color:#fff;font-family:'verdana' , 'helvetica' , sans-serif;font-size:16px"><div>Hi,</div><div><br /></div><div>I have a dataset in EPSG:4326 which is a 0-360 degree longitude space (which EPSG tells me is a valid use of this projection).</div><div><br /></div><div>I also have one in EPSG:3994 (Mercator 41).</div><div><br /></div><div>QGIS cannot correctly display both of these together in a single map. If I use a project CRS of EPSG:4326 the initial dataset renders correctly, but the EPSG:3994 dataset breaks at 180 degrees.</div><div><br /></div><div dir="ltr">If I use a project CRS of EPSG:3994, then the situation is reversed. The fundamental issue is a discontinuity at 180 degrees longitude.</div><div dir="ltr"><br /></div><div dir="ltr">Most lat/long datasets I use around 180 (most of what I do) are 0-360 so they natively plot correctly.</div><div dir="ltr"><br /></div><div dir="ltr">I'm not discussing the issues of polygons across 180 (& 0) degrees longitude - this is a more complex issue. Points & lines, however are more straightforward (Ha!)</div><div dir="ltr"><br /></div><div dir="ltr">There is a Postgis function ST_Shift_Longitude() which toggles between +-180 & 0-360 longitude spaces for coords in the W hemisphere. An ideal solution would perhaps be to have a similar user specified toggle in QGIS for datasets (or projects) with units degrees, to switch the applied (as opposed to recorded) X coordinate between these.</div><div dir="ltr"><br /></div><div dir="ltr">This would allow the EPSG:4326 dataset to be switched to a +-180 space before the coords are sent to Proj for transforming, & the EPSG:3994 dataset to be presented in a 0-360 space in a project using the EPSG:4326 CRS.</div><div dir="ltr"><br /></div><div dir="ltr">I've no idea how difficult this might be to implement, possibly a pretty fundamental paradigm shift in how coordinates & CRS's are managed... but it would be nice if QGIS was one of the first GIS tools to start addressing this issue :-)</div><div dir="ltr"><br /></div><div dir="ltr"><br /></div><div dir="ltr">Any comments/suggestions as to how this issue could best be addressed?</div><div dir="ltr"><br /></div><div dir="ltr">Thanks,</div><div dir="ltr"><br /></div><div dir="ltr"> Brent Wood<br /></div></div><br />_______________________________________________
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