<div dir="ltr">👍<div>logical and clear</div><div>thanks</div><div><br clear="all"><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr">Marc MILLAS<div>Senior Architect</div><div>+33607850334</div><div><a href="http://www.mokadb.com" target="_blank">www.mokadb.com</a></div><div><br></div></div></div></div></div></div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Feb 9, 2023 at 6:16 PM chris hermansen <<a href="mailto:clhermansen@gmail.com">clhermansen@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr">Mark and list;<br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Feb 9, 2023 at 8:24 AM Marc Millas via QGIS-User <<a href="mailto:qgis-user@lists.osgeo.org" target="_blank">qgis-user@lists.osgeo.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Hello,<div><br></div><div>I got an autocad dxf file describing objects in Djibouti.</div><div>no pb to load it in qgis as a vector layer.</div><div>but... the srid seems to be 0 and QGIS ask for a valid ref</div><div>as the data looks x,y, I did try epsg 32638, which is standard in Djibouti.</div><div>loads fine... but the objects are around 200km west of where they should be.</div><div><br></div><div>any idea ?</div></div><br></blockquote><div>Perhaps your dxf data is not georeferenced. It may be in rectangular coordinates (x, y) representing metres from some origin point that makes sense when thinking of it as a drawing (like the centre of the drawing or the southwest corner or a nearby landmark).</div><div><br></div><div>Therefore when you assign a projection to it, its origin point will be at the origin of the projection. In your case using EPSG 32638, that is UTM zone 38N whose centre coordinates are <span>500000</span> <span>4649776</span> (see <a href="https://epsg.io/32638" target="_blank">https://epsg.io/32638</a>).</div><div><br></div><div>The origin point of your drawing will be in that coordinate system; (0,0) will be 500000 metres west of 45° east longitude and on the equator; in other words, 40.511256° east longitude and 0° latitude.<br></div><div><br></div><div>The latitude and longitude of Djibouti City is 11.572076, 43.145645 (see <a href="https://www.latlong.net/place/djibouti-city-djibouti-24884.html" target="_blank">https://www.latlong.net/place/djibouti-city-djibouti-24884.html</a>). You can see that your origin point (0,0) in UTM zone 38M is 2.634389° west and 11.572076° south of Djibouti City.<br></div><div><br></div><div>Working back to UTM coordinates, in UTM zone 38N Djibouti City is 297791.1138793365 east and 1279891.9276488272 north (see <a href="https://epsg.io/transform#s_srs=4326&t_srs=32638&x=43.1456450&y=11.5720760" target="_blank">https://epsg.io/transform#s_srs=4326&t_srs=32638&x=43.1456450&y=11.5720760</a>)</div><div><br></div><div>If your DXF data coordinates - say the centre of the drawing file - aren't somewhere around (297791,1279892) then you need to transform your data as you import it (or afterward).<br></div><div><br></div><div>Please read these articles</div><div><br></div><div><a href="https://opengislab.com/blog/tag/DWG+DXF+QGIS" target="_blank">https://opengislab.com/blog/tag/DWG+DXF+QGIS</a></div></div><div><a href="https://gis.stackexchange.com/questions/22691/georeferencing-dxf-using-qgis" target="_blank">https://gis.stackexchange.com/questions/22691/georeferencing-dxf-using-qgis</a></div><div><a href="https://www.mkrgeo-blog.com/good-solution-to-georeferencing-the-autocad-dwg-drawing-in-qgis-3x/" target="_blank">https://www.mkrgeo-blog.com/good-solution-to-georeferencing-the-autocad-dwg-drawing-in-qgis-3x/</a></div><div><br></div><div>which will provide you with some ideas and more background info.<br></div><br>-- <br><div dir="ltr"><div dir="ltr">Chris Hermansen · clhermansen "at" gmail "dot" com<br><br>C'est ma façon de parler.</div></div></div>
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