<html><head></head><body><div style="color:#000; background-color:#fff; font-family:verdana, helvetica, sans-serif;font-size:16px"><div id="yui_3_16_0_1_1468385772141_686289">Hi,</div><div id="yui_3_16_0_1_1468385772141_686365"><br></div><div id="yui_3_16_0_1_1468385772141_686370">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 id="yui_3_16_0_1_1468385772141_686371"><br></div><div id="yui_3_16_0_1_1468385772141_686372">I also have one in EPSG:3994 (Mercator 41).</div><div id="yui_3_16_0_1_1468385772141_686373"><br></div><div id="yui_3_16_0_1_1468385772141_686374">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 id="yui_3_16_0_1_1468385772141_686393"><br></div><div id="yui_3_16_0_1_1468385772141_686570" 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 id="yui_3_16_0_1_1468385772141_686563" dir="ltr"><br></div><div id="yui_3_16_0_1_1468385772141_686569" 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 id="yui_3_16_0_1_1468385772141_686564" dir="ltr"><br></div><div id="yui_3_16_0_1_1468385772141_686571" 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 id="yui_3_16_0_1_1468385772141_686730" dir="ltr"><br></div><div id="yui_3_16_0_1_1468385772141_686565" 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 id="yui_3_16_0_1_1468385772141_686566" dir="ltr"><br></div><div id="yui_3_16_0_1_1468385772141_686572" 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 id="yui_3_16_0_1_1468385772141_686643" dir="ltr"><br></div><div id="yui_3_16_0_1_1468385772141_686644" 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 id="yui_3_16_0_1_1468385772141_686761" dir="ltr"><br></div><div id="yui_3_16_0_1_1468385772141_686764" dir="ltr"><br></div><div id="yui_3_16_0_1_1468385772141_686763" dir="ltr">Any comments/suggestions as to how this issue could best be addressed?</div><div id="yui_3_16_0_1_1468385772141_686772" dir="ltr"><br></div><div dir="ltr">Thanks,</div><div id="yui_3_16_0_1_1468385772141_686773" dir="ltr"><br></div><div dir="ltr"> Brent Wood<br></div></div></body></html>