<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div></div><div><br></div><div><br>Le 18 mai 2018 à 00:28, <<a href="mailto:listsen@0x906.com">listsen@0x906.com</a>> <<a href="mailto:listsen@0x906.com">listsen@0x906.com</a>> a écrit :<br><br></div><blockquote type="cite"><div>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<p>I haven't been able to open the dataset but going through the discussion I would like to offer some assistance since I believe there are some misconceptions here:<br> <br> First, the data has nothing to do with the NAD27 / NAD83 datum's since these are North American datum's and they don't apply I believe in South America. Moreover, the separation between NAD27 to NAD83 is about 100m. I think Carlos mention something like being 400m off.<br> <br> Another point of confusion is about the projection of Google Earth. Google is using a Web Mercator projection based on a perfect sphere. This has nothing to do with the UTM that has already incorporate the Earth Flattening values into the Northing and Easting equations.<br> <br> If I find some time tomorrow, I will come back and give the proper equations showing the difference between Google's projection and UTM.<br> <br> -0x906</p>
<p><br></p>
<p>On 2018-05-17 19:53, Carlos Henrique Grohmann de Carvalho wrote:</p>
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0"><!-- html ignored --><!-- head ignored --><!-- meta ignored -->
<div dir="ltr">Thanks for the input Nicolas
<div> </div>
<div>These are official maps so the utm grid is ok. I figured that I was using a linear transformation, with the option to just create the world file, which works for control points at the corners (lat/long), since the boundaries of the map is defined by latitude/longitude. With UTM, this simple transformation won't work, but TPS will give the correct results.</div>
<div> </div>
<div>Carlos</div>
<div> </div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Thu, May 17, 2018 at 7:28 PM, Nicolas Cadieux <span><<a href="mailto:nicolas.cadieux@archeotec.ca">nicolas.cadieux@archeotec.ca</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0 0 0 .8ex; border-left: 1px #ccc solid; padding-left: 1ex;">
<div dir="auto">
<div> </div>
<div>Hi,</div>
<div>The utm grid is way off or we have the wrong epsg code. If you geofence using 2 points (linear algo) using a service like google earth, you will see the distortion. The long lat coordinate are probably ok but I did not test them.</div>
<div> </div>
<div>You can either use the long lat or use more points. With 4 points and using the thin plate spline, I got good results.</div>
<div>Nicolas</div>
<div>
<div class="h5">
<div><br>Le 17 mai 2018 à 12:42, Carlos Henrique Grohmann de Carvalho <<a href="mailto:carlos.grohmann@gmail.com">carlos.grohmann@gmail.com</a>> a écrit :<br><br></div>
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">
<div>
<div dir="ltr">Thanks Nicolas, but the misalignment still persists. OTF is off, project has same CRS as data (epsg 29192). There is a ~400m difference in the N-S direction.
<div> </div>
<div>Carlos</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Thu, May 17, 2018 at 1:28 PM, Nicolas Cadieux <span><<a href="mailto:nicolas.cadieux@archeotec.ca">nicolas.cadieux@archeotec.ca</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0 0 0 .8ex; border-left: 1px #ccc solid; padding-left: 1ex;">
<div dir="auto">
<div> </div>
<div>Hi,</div>
<div>Disable projection on the fly. Make sure the project is in the same CRS as your maps.</div>
<div>Nicolas</div>
<div>
<div class="m_5331241165982910871m_1909886288506383736h5">
<div><br>Le 17 mai 2018 à 12:14, Carlos Henrique Grohmann de Carvalho <<a href="mailto:carlos.grohmann@gmail.com">carlos.grohmann@gmail.com</a>> a écrit :<br><br></div>
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">
<div>
<div dir="ltr"><span style="font-size: 12.800000190734863px;">Hello all</span>
<div style="font-size: 12.800000190734863px;"> </div>
<div style="font-size: 12.800000190734863px;">I have two pngs of topographic maps from southeastern Brazil (a zip file with images and points is available here: <a href="https://www.dropbox.com/s/mexeh4be46pgsk6/images_georef.zip?dl=0" target="_blank" rel="noopener noreferrer">https://www.dropbox.com/<wbr>s/mexeh4be46pgsk6/images_geore<wbr>f.zip?dl=0</a>)</div>
<div style="font-size: 12.800000190734863px;"> </div>
<div style="font-size: 12.800000190734863px;">I'm trying to georeference them, but with partial success only. In this image (<a href="https://www.dropbox.com/s/37xxqp4fkwpdyqh/utm_error.png?dl=0" target="_blank" rel="noopener noreferrer">https://www.dropbox.com/s/37x<wbr>xqp4fkwpdyqh/utm_error.png?dl=<wbr>0</a>) you can see that the X coordinate is fine, but the Y coordinate of the two maps won't match.</div>
<div style="font-size: 12.800000190734863px;"> </div>
<div style="font-size: 12.800000190734863px;">Both maps use South American Datum 1969. I selected points near the edges, and used the UTM values. </div>
<div style="font-size: 12.800000190734863px;"> </div>
<div style="font-size: 12.800000190734863px;">Interestingly, if I use Lat/Long, and place the points at the corners, using decimal degrees, the maps align perfectly.</div>
<div style="font-size: 12.800000190734863px;"> </div>
<div style="font-size: 12.800000190734863px;"> </div>
<div style="font-size: 12.800000190734863px;">Any help is appreciated</div>
<br clear="all">
<div> </div>
-- <br>
<div class="m_5331241165982910871m_1909886288506383736m_2947533340930390789gmail_signature">
<div dir="ltr">Prof. Carlos Henrique Grohmann<br>Institute of Energy and Environment - Univ. of São Paulo, Brazil
<div>- Digital Terrain Analysis | GIS | Remote Sensing - </div>
<div> </div>
<div><a href="http://carlosgrohmann.com/" target="_blank" rel="noopener noreferrer">http://carlosgrohmann.com</a></div>
<div><a style="font-size: 13px; color: #1155cc;" href="http://orcid.org/0000-0001-5073-5572" target="_blank" rel="noopener noreferrer">http://orcid.org/0000-0001-507<wbr>3-5572</a><br>
<div>________________<br>Can't stop the signal.</div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
</div>
</div>
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">
<div><span>______________________________<wbr>_________________</span><br><span>Qgis-user mailing list</span><br><span><a href="mailto:Qgis-user@lists.osgeo.org">Qgis-user@lists.osgeo.org</a></span><br><span>List info: <a href="https://lists.osgeo.org/mailman/listinfo/qgis-user" target="_blank" rel="noopener noreferrer">https://lists.osgeo.org/mailma<wbr>n/listinfo/qgis-user</a></span><br><span>Unsubscribe: <a href="https://lists.osgeo.org/mailman/listinfo/qgis-user" target="_blank" rel="noopener noreferrer">https://lists.osgeo.org/mailma<wbr>n/listinfo/qgis-user</a></span></div>
</blockquote>
</div>
</blockquote>
</div>
<br><br clear="all">
<div> </div>
-- <br>
<div class="m_5331241165982910871m_1909886288506383736gmail_signature">
<div dir="ltr">Prof. Carlos Henrique Grohmann<br>Institute of Energy and Environment - Univ. of São Paulo, Brazil
<div>- Digital Terrain Analysis | GIS | Remote Sensing - </div>
<div> </div>
<div><a href="http://carlosgrohmann.com/" target="_blank" rel="noopener noreferrer">http://carlosgrohmann.com</a></div>
<div><a style="font-size: 13px; color: #1155cc;" href="http://orcid.org/0000-0001-5073-5572" target="_blank" rel="noopener noreferrer">http://orcid.org/0000-0001-507<wbr>3-5572</a><br>
<div>________________<br>Can't stop the signal.</div>
</div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
</div>
</div>
</div>
</blockquote>
</div>
<br><br clear="all">
<div> </div>
-- <br>
<div class="gmail_signature">
<div dir="ltr">Prof. Carlos Henrique Grohmann<br>Institute of Energy and Environment - Univ. of São Paulo, Brazil
<div>- Digital Terrain Analysis | GIS | Remote Sensing - </div>
<div> </div>
<div><a href="http://carlosgrohmann.com/" target="_blank" rel="noopener noreferrer">http://carlosgrohmann.com</a></div>
<div><a style="font-size: 13px; color: #1155cc;" href="http://orcid.org/0000-0001-5073-5572" target="_blank" rel="noopener noreferrer">http://orcid.org/0000-0001-5073-5572</a><br>
<div>________________<br>Can't stop the signal.</div>
</div>
</div>
</div>
</div>
<br>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">_______________________________________________<br> Qgis-user mailing list<br> <a href="mailto:Qgis-user@lists.osgeo.org">Qgis-user@lists.osgeo.org</a><br> List info: <a href="https://lists.osgeo.org/mailman/listinfo/qgis-user" target="_blank" rel="noopener noreferrer">https://lists.osgeo.org/mailman/listinfo/qgis-user</a><br> Unsubscribe: <a href="https://lists.osgeo.org/mailman/listinfo/qgis-user" target="_blank" rel="noopener noreferrer">https://lists.osgeo.org/mailman/listinfo/qgis-user</a></div>
</blockquote>
<p><br></p>
</div></blockquote></body></html>