<meta http-equiv="content-type" content="text/html; charset=utf-8"><div></div><div>Hi </div><div>See below for answers,</div><div><br>Le 16 nov. 2016 à 05:00, Alexander James Metcalfe [via <a href="http://OSGeo.org" target="_top" rel="nofollow" link="external">OSGeo.org</a>] <<a href="/user/SendEmail.jtp?type=node&node=5296041&i=0" target="_top" rel="nofollow" link="external">[hidden email]</a>> a écrit :<br><br></div><blockquote style='border-left:2px solid #CCCCCC;padding:0 1em' type="cite"><div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">Hi QGIS community, </span></div>
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<p style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt"><span style="font-size:12pt">My reason for using QGIS is relatively simple. I could really use some help to set me straight and I would be very grateful.</span><br>
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<li>My study area is <span style="font-size:12pt">D</span><span style="font-size:12pt">uncan Down in </span><span style="font-size:12pt">W</span><span style="font-size:12pt">hitstable, UK. I have attempted to</span><span style="font-size:12pt"> </span><span style="font-size:12pt">geo-reference
a hi-res image of this site f</span><span style="font-size:12pt">ro</span><span style="font-size:12pt">m Google Earth.</span><span style="font-size:12pt"> </span></li><li>I want to over lay this with a grid to represent quadrats for vegetation mapping and random sampling.<span style="font-size:12pt"> </span><br>
</li><li><span style="font-size:12pt">I'll use images taken from these stages to include in my methods section of my MSc dissertation/thesis</span></li></ul>
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<div style="color:rgb(33,33,33); font-size:15px"><font face="Calibri, Arial, Helvetica, sans-serif"><span style="font-size:12pt">My problems are: </span></font></div>
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<li style="color:rgb(33,33,33); font-size:15px">That, in georeferencing the google earth image (with the georeferencing tool) I have been able to get it to line up just about right with the openlayers google earth plugin visualisation. I do this by entering
coordinates gained from google earth manually into the georeferencer. </li></ul></div></div></div></div></div></div></blockquote><div>I hope you are using the Google Earth Image just for visualisation. They are not good for any kind of spectral analysis.</div><div><br></div><br><blockquote style='border-left:2px solid #CCCCCC;padding:0 1em' type="cite"><div><div id="divtagdefaultwrapper" style="font-size:12pt;color:#000000;font-family:Calibri,Arial,Helvetica,sans-serif;" dir="ltr"><div style="color: rgb(0, 0, 0);"><div><div id="divtagdefaultwrapper" dir="ltr" style="font-size:12pt; color:#000000; font-family:Calibri,Arial,Helvetica,sans-serif"><div>
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<li>Unfortunately when I go to create a vector grid (via research tools) a pop-up tells me the CRS for the raster (I am creating the grid for, the study site) and the project are different. I can get it to create a grid but it is always rectangular rather than
square. I understand that this might be a result of on-the-fly CRS transformation. I'm not sure whether this is somehow incorrect or will affect my ability to properly map GPS points gained in the field work. </li></ul></div></div></div></div></div></div></blockquote><div><br></div>Yes, if your project is in long /lat, the grid will be a rectangle and not a square unless you are on the equator.<br><blockquote style='border-left:2px solid #CCCCCC;padding:0 1em' type="cite"><div><div id="divtagdefaultwrapper" style="font-size:12pt;color:#000000;font-family:Calibri,Arial,Helvetica,sans-serif;" dir="ltr"><div style="color: rgb(0, 0, 0);"><div><div id="divtagdefaultwrapper" dir="ltr" style="font-size:12pt; color:#000000; font-family:Calibri,Arial,Helvetica,sans-serif"><div>
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<li><font face="Calibri, Arial, Helvetica, sans-serif" style="color:rgb(33,33,33); font-size:15px"><span style="font-size:12pt">The project is WG 84 / Pseudo Mercator EPSG: 3857 and the raster is </span></font><span style="color:rgb(33,33,33); font-size:15px">WG
84 / Pseudo Mercator EPSG: 4326. When they are like this they are aligned. When I change the CRS for the raster to match the project (e.g. from 4326 to 3857) it ends up being transported to the somewhere else off the coast of South America! And, it is very
skewed. </span><br></li></ul></div></div></div></div></div></div></blockquote><div>You cannot just change the CRS. You need to reproject the raster. To do that, use gdal warp in the raster menu. Just changing the crs in the layer is only good if you have made an error and want to correct that (for example, change the utm zone).</div><blockquote style='border-left:2px solid #CCCCCC;padding:0 1em' type="cite"><div><div id="divtagdefaultwrapper" style="font-size:12pt;color:#000000;font-family:Calibri,Arial,Helvetica,sans-serif;" dir="ltr"><div style="color: rgb(0, 0, 0);"><div><div id="divtagdefaultwrapper" dir="ltr" style="font-size:12pt; color:#000000; font-family:Calibri,Arial,Helvetica,sans-serif"><div><ul><li>
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<div style="color:rgb(33,33,33); font-size:15px">I feel like I am trying to do a simple thing here and it's going wrong at every turn....<br>
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<div style="color:rgb(33,33,33); font-size:15px">Kind and hopeful regards, </div>
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<div style="color:rgb(33,33,33); font-size:15px">Alex</div>
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