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<p><font size="+1">Hi all,</font></p>
<p><font size="+1">After some additional tests and readings I think
I finally have this figured out. For the record:<br>
</font></p>
<p><font size="+1">- The values of the coordinates of rHealPix are
not radians. They are projected and in units of the authalic
radius. By using all the time +a=1 in my tests they looked
similar and that got me confused.<br>
</font></p>
<p><font size="+1">- The authalic sphere of the WGS84 ellipsoid with
semi-major axis == 1 does not have a radius of 1 but slightly
smaller. This would be the reason why some values on the "edges"
were not converted. If I use +a=1.00336409 with +ellps=WGS84
(ratio between its semi-major and semi-minor axes) the authalic
sphere has a radius just barely larger than 1 and I can convert
those points on the "edges".</font></p>
<font size="+1">
</font>
<p><font size="+1">Best regards,</font></p>
<p><font size="+1"> Rubén</font><br>
</p>
<div class="moz-cite-prefix">El 9/10/18 a las 11:21, Thomas Knudsen
escribió:<br>
</div>
<blockquote type="cite"
cite="mid:CAH0YoENkTNHEnncMe=8gHfZMdKs7prGNGm6aS4D3MGRR8k8YqA@mail.gmail.com">
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<div>Rubén,</div>
<div><br>
</div>
<div>first, I recommend not mixing "minus style" general
options with "plus style" projection definitions. It works
for proj and cs2cs, but will not for the next generation
tool, cct, so I suggest saying:</div>
<div><br>
</div>
<div>proj -EIf '%.4f' +proj=rhealpix +lon_0=0 +a=1
+ellps=WGS84 +north_square=0 +south_square=0</div>
<div><br>
</div>
<div>second: I can replicate your results, but...</div>
<div><br>
</div>
<div>third: I have no idea what it means, and cannot help -
any rHealpix users here? Please speak up!</div>
<div><br>
</div>
<div>/thomas<br>
</div>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr">Den tir. 9. okt. 2018 kl. 10.19 skrev Rubén Béjar
<<a href="mailto:rbejar@unizar.es" target="_blank"
moz-do-not-send="true">rbejar@unizar.es</a>>:<br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#660000" bgcolor="#FFFFFF">
<p><font size="+1"><font face="Helvetica, Arial, sans-serif">Hi
people, <br>
</font></font></p>
<p><font size="+1"><font face="Helvetica, Arial, sans-serif">I
am having some problems with the rHealPix projection
and maybe you can help me.</font></font></p>
<p><font size="+1"><font face="Helvetica, Arial, sans-serif">In
(0,0)-rHealPix (i.e. north_square = south_square = 0),
I understand that the top left corner is (-PI,
3*PI/4).<br>
</font></font></p>
<p><font size="+1"><font face="Helvetica, Arial, sans-serif">However
trying to project that point to lon-lat WGS84 fails.</font></font></p>
<p><font size="+1"><font face="Helvetica, Arial, sans-serif">I
am running proj 5.2.0 (September 15th, 2018) in a
terminal in Ubuntu 18.04 (I have compiled it from
sources, I am not using the older version from the
repositories).<br>
</font></font></p>
<p><font size="+1"><font face="Helvetica, Arial, sans-serif">I
assumed that it could be due to some
tolerances/epsilon issues. However it does not seem to
be so. I have tried with this command: <br>
</font></font></p>
<p><font size="+1"><font face="Helvetica, Arial, sans-serif">proj
+proj=rhealpix -f '%.4f' -I +lon_0=0 +a=1 +ellps=WGS84
+north_square=0 +south_square=0 -E <br>
</font></font></p>
<p><font size="+1"><font face="Helvetica, Arial, sans-serif">and
some of the results I get are these:</font></font></p>
<p><font size="+1"><font face="Helvetica, Arial, sans-serif">-3.14
2.35<br>
-3.14 2.35 * *<br>
-3.13 2.34<br>
-3.13 2.34 90.3176 42.4654<br>
-3.138 2.348<br>
-3.138 2.348 90.3144 41.9431<br>
-3.139 2.349<br>
-3.139 2.349 * *<br>
</font></font></p>
<p><br>
<font size="+1"><font face="Helvetica, Arial, sans-serif">So
even after "pushing" the top left corner to the right
(from -PI to -3.14, big difference) and down (from
3*PI/4 to 2.35, again big difference) I still don't
get a conversion. The closest to the "real" point that
seems to work is around (-3.138, 2.349) which is far
from that corner (much further than a tolerance).</font></font></p>
<p><font size="+1"><font face="Helvetica, Arial, sans-serif">This
corner is a simple, easily reproducible case. I am
having similar problems close to the edges of the N
square (and possibly close to some of the edges of
other squares too).<br>
</font></font></p>
<p><font size="+1"><font face="Helvetica, Arial, sans-serif">Am
I doing something wrong, or is this a problem with
rHeallPix in Proj.4?</font></font></p>
<p><font size="+1"><font face="Helvetica, Arial, sans-serif">Thanks
in advance!</font></font></p>
<p><font size="+1"><font face="Helvetica, Arial, sans-serif">
Rubén<br>
</font></font></p>
<p><br>
</p>
<br>
</div>
</blockquote>
</div>
</blockquote>
<div class="moz-signature">-- <br>
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<p style="margin:0px; font-size:11pt; font-family:Arial,
sans-serif; color:#223D71;"> Dr. Rubén Béjar<br>
<a style="margin:0px; font-size:11pt; font-family:Arial,
sans-serif; color:#223D71; text-decoration: none"
href="https://www.unizar.es"><b>Universidad</b> Zaragoza</a><br>
<a style="margin:0px; font-size:10pt; font-family:Arial,
sans-serif; color:#223D71; text-decoration: none"
href="https://www.iaaa.es/"><span style="font-style:italic"
lang="en">Advanced Information Systems Laboratory</span></a><br>
<a style="margin:0px; font-size:10pt; font-family:Arial,
sans-serif; color:#223D71; text-decoration: none"
href="http://i3a.unizar.es/"><span style="font-style:italic"
lang="en">Aragon Institute of Engineering Research</span></a><br>
<br>
<a style="margin:0px; font-size:10pt; font-family:Arial,
sans-serif; color:#223D71; text-decoration: none"
href="mailto:rbejar@unizar.es">rbejar@unizar.es</a> <a
style="margin:0px; font-size:10pt; font-family:Arial,
sans-serif; color:#223D71; text-decoration: none"
href="https://twitter.com/rubejar">(@rubejar in Twitter)</a><br>
<a style="margin:0px; font-size:10pt; font-family:Arial,
sans-serif; color:#B04F00; text-decoration: none"
href="https://www.rubenbejar.com"><b>rubenbejar</b>.com</a>
<br>
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