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<p>Hi Carlos:</p>
I georeferenced 2 screen shots of your maps and obtained good
results. I would have a close look at the coordinates of your
ground control points and make sure you selected the utm grid
intersection as a control point versus the corner of the mapsheet
which is a lat/long grid. It is easy to make a simple mistake<br>
<br>
Kirk<br>
<p><br>
</p>
<br>
<div class="moz-cite-prefix">On 5/17/2018 8:53 PM, Carlos Henrique
Grohmann de Carvalho wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAEiUsPtLbYqoDRSjjorC-_TGH3L0StKRoVOtuEh59X-K+1DU4A@mail.gmail.com">
<meta http-equiv="Context-Type" content="text/html; charset=UTF-8">
<div dir="ltr">Thanks for the input Nicolas
<div><br>
</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><br>
</div>
<div>Carlos</div>
<div><br>
</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Thu, May 17, 2018 at 7:28 PM,
Nicolas Cadieux <span dir="ltr"><<a
href="mailto:nicolas.cadieux@archeotec.ca" target="_blank"
moz-do-not-send="true">nicolas.cadieux@archeotec.ca</a>></span>
wrote:<br>
<blockquote class="gmail_quote">
<div dir="auto">
<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><br>
</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>
<span class="HOEnZb">
<div>Nicolas</div>
</span>
<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"
target="_blank" moz-do-not-send="true">carlos.grohmann@gmail.com</a>>
a écrit :<br>
<br>
</div>
<blockquote type="cite">
<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><br>
</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 dir="ltr"><<a
href="mailto:nicolas.cadieux@archeotec.ca" target="_blank"
moz-do-not-send="true">nicolas.cadieux@archeotec.ca</a>></span>
wrote:<br>
<blockquote class="gmail_quote">
<div dir="auto">
<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" target="_blank"
moz-do-not-send="true">carlos.grohmann@gmail.com</a>>
a écrit :<br>
<br>
</div>
<blockquote type="cite">
<div>
<div dir="ltr"><span>Hello all</span>
<div><br>
</div>
<div>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"
moz-do-not-send="true">https://www.dropbox.com/<wbr>s/mexeh4be46pgsk6/images_geore<wbr>f.zip?dl=0</a>)</div>
<div><br>
</div>
<div>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"
moz-do-not-send="true">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><br>
</div>
<div>Both maps use South
American Datum 1969. I
selected points near the
edges, and used the UTM
values. </div>
<div><br>
</div>
<div>Interestingly, if I use
Lat/Long, and place the
points at the corners, using
decimal degrees, the maps
align perfectly.</div>
<div><br>
</div>
<div><br>
</div>
<div>Any help is appreciated</div>
<br>
<div><br>
</div>
-- <br>
<div
class="m_5331241165982910871m_1909886288506383736m_2947533340930390789gmail_signature"
data-smartmail="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><br>
</div>
<div><a
href="http://carlosgrohmann.com/"
target="_blank"
moz-do-not-send="true">http://carlosgrohmann.com</a></div>
<div><a
href="http://orcid.org/0000-0001-5073-5572"
target="_blank"
moz-do-not-send="true">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>
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<blockquote type="cite">
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<div><br>
</div>
-- <br>
<div
class="m_5331241165982910871m_1909886288506383736gmail_signature"
data-smartmail="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><br>
</div>
<div><a href="http://carlosgrohmann.com/"
target="_blank" moz-do-not-send="true">http://carlosgrohmann.com</a></div>
<div><a
href="http://orcid.org/0000-0001-5073-5572"
target="_blank" moz-do-not-send="true">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>
<div><br>
</div>
-- <br>
<div class="gmail_signature" data-smartmail="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><br>
</div>
<div><a href="http://carlosgrohmann.com/" target="_blank"
moz-do-not-send="true">http://carlosgrohmann.com</a></div>
<div><a href="http://orcid.org/0000-0001-5073-5572"
target="_blank" moz-do-not-send="true">http://orcid.org/0000-0001-5073-5572</a><br>
<div>________________<br>
Can’t stop the signal.</div>
</div>
</div>
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<br>
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<pre class="moz-signature" cols="72">--
Kirk Schmidt, MScF, BScF, RPF
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Nortek Resource Solutions Inc.
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