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<p>Roberto,</p>
<p>the proj utility only works with a projection operation, where
input geographic coordinates are expressed in the base CRS of the
projected CRS (which is EPSG:4162 "Korean 1985" here), and doesn't
apply any datum transformation. So the equivalent of your proj
invokation with cs2cs would be cs2cs +init=epsg:4162 +to
+init=epsg:5174</p>
<p>If you use EPSG:4326 as the input CRS, then there will be a datum
shift from EPSG:4326 to EPSG:4162</p>
<p>Regarding the pipeline output by projinfo -s -t, you can't use it
with the proj utility, which is a historic one and is aimed only
at understanding +proj={projection_id} style of PROJ strings. You
should rather use the newer cct utility.</p>
<p>Even<br>
</p>
<div class="moz-cite-prefix">Le 18/09/2021 à 14:13, Roberto Toldo a
écrit :<br>
</div>
<blockquote type="cite"
cite="mid:CADgX5JxBL1dUdbC+J8CpEPZC1MA75hhPoCV3SVA3PNZX9M3qfQ@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">I was able to get the actual pipeline
transformation used by "cs2cs" by running: <br>
<div><i>projinfo -s EPSG:4326 -t EPSG:5174</i></div>
<div><br>
</div>
<div>Still, I'm having problems using the output proj string:<br>
<i>+proj=pipeline<br>
+step +proj=axisswap +order=2,1<br>
+step +proj=unitconvert +xy_in=deg +xy_out=rad<br>
+step +proj=push +v_3<br>
+step +proj=cart +ellps=WGS84<br>
+step +inv +proj=molobadekas +x=-145.907 +y=505.034
+z=685.756 +rx=-1.162<br>
+ry=2.347 +rz=1.592 +s=6.342 +px=-3159521.31
+py=4068151.32<br>
+pz=3748113.85 +convention=coordinate_frame<br>
+step +inv +proj=cart +ellps=bessel<br>
+step +proj=pop +v_3<br>
+step +proj=tmerc +lat_0=38 +lon_0=127.002890277778 +k=1
+x_0=200000<br>
+y_0=500000 +ellps=bessel<br>
+step +proj=axisswap +order=2,1</i></div>
<div><br>
</div>
<div>The error I get is "can't initialize operations that take
non-angular input coordinates". If I remove the "unitconvert"
step, I can run proj bin, but I get wrong results (even if I
manually convert the input from degree to radians). Any
suggestions?</div>
<div><br>
</div>
<div>Many thanks,</div>
<div>Roberto</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Fri, Sep 17, 2021 at 9:35
AM Roberto Toldo <<a href="mailto:roberto.toldo@3dflow.net"
moz-do-not-send="true">roberto.toldo@3dflow.net</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!<br>
<br>
I found some issues/differences from the "proj" bin and
"cs2cs" bin utilities. I'm using the last version, directly
compiled from Github.<br>
Probably it's something due to my inexperience with the
library, so please bear with me :)<br>
<br>
Specifically, I was trying to convert coordinates from
geodetic to EPSG:5174 ( Korean 1985 / Modified Central
Belt).<br>
<br>
I used proj with the parameters extracted from "projinfo
EPSG:5174":<br>
proj +proj=tmerc +lat_0=38 +lon_0=127.002890277778 +k=1
+x_0=200000 +y_0=500000 +ellps=bessel +units=m +no_defs<br>
<br>
and then cs2cs with direct conversion parameters:<br>
cs2cs +init=epsg:4326 +to +init=epsg:5174<br>
<br>
However, I obtain quite different results.<br>
<br>
For example, If I use lat_0 and lon_0 as input
(127.002890277778, 38), I obtain exactly false_easting and
false_northing (200000, 500000) when using proj4 (as
expected), while I obtain something different when using
cs2cs (200185.04 499695.19). <br>
I would be expecting the same results. I tried with other
coordinate systems (e.g., EPSG:32633 UTM zone 33N), and I
noticed no differences between proj and cs2cs results.<br>
Can anybody help me understand what the reason for the
differences is? Are the parameters used internally by cs2cs
different for EPSG:5174? I also tried setting the accuracy,
but it doesn't seem to work.<br>
<div><br>
</div>
<div>Thanks,</div>
<div>Roberto</div>
<div><br>
</div>
</div>
</blockquote>
</div>
<br clear="all">
<br>
-- <br>
<div dir="ltr" class="gmail_signature">
<div dir="ltr"><span
style="font-family:arial,helvetica,sans-serif"><font
size="1">Roberto Toldo<br>
Technical Director & Co-founder | 3Dflow srl</font><br>
<font size="1">+39 </font></span><span
style="font-family:arial,helvetica,sans-serif"><font
size="1">045 4500109 | <a
href="mailto:roberto.toldo@3dflow.net" target="_blank"
moz-do-not-send="true">roberto.toldo@3dflow.net</a> | <a
href="http://www.3dflow.net" target="_blank"
moz-do-not-send="true">http://www.3dflow.net</a></font><font
size="1">
</font></span></div>
</div>
<br>
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