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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:15.0pt"><span style="mso-ligatures:none;mso-fareast-language:EN-IN">Dear Proj Team,<br>
I hope this email finds you well. I am writing to seek guidance on how to project a point from one ellipsoid to another ellipsoid using the Proj library.<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:15.0pt"><span style="mso-ligatures:none;mso-fareast-language:EN-IN">I have been working on a geospatial project that requires converting coordinates between different ellipsoids. After some research,
I discovered that the Proj library is a widely used and powerful tool for geospatial data transformations. However, I am currently facing some challenges in understanding and implementing the ellipsoid projection functionality.<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:15.0pt"><span style="mso-ligatures:none;mso-fareast-language:EN-IN">I would greatly appreciate it if you could provide me with some guidance on how to accomplish this task using the Proj library.
Specifically, I would like to know:<o:p></o:p></span></p>
<ol start="1" type="1">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l1 level1 lfo2">
<span style="mso-ligatures:none;mso-fareast-language:EN-IN">I want to project a 3d point which is in wgs84 to an airy ellipsoid.<br>
I did as shown below. But I am getting incorrect values and height of the point is also not changing.<br>
<br>
</span><span style="font-size:9.5pt;font-family:Consolas;color:#2B91AF">PJ</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> *Src = proj_create(C,
</span><span style="font-size:9.5pt;font-family:Consolas;color:#A31515">"+proj=geocent +datum=WGS84 +type=crs"</span><span style="font-size:9.5pt;font-family:Consolas;color:black">);</span><span style="mso-ligatures:none;mso-fareast-language:EN-IN"><o:p></o:p></span></li></ol>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="font-size:9.5pt;font-family:Consolas;color:#2B91AF">PJ</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> *Targ_Coor = proj_create(C,
</span><span style="font-size:9.5pt;font-family:Consolas;color:#A31515">"+proj=geocent +ellps=airy +type=crs"</span><span style="font-size:9.5pt;font-family:Consolas;color:black">);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:36.0pt;text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:blue">auto</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> P2G = proj_create_crs_to_crs_from_pj(C, Src, Targ_Coor,
</span><span style="font-size:9.5pt;font-family:Consolas;color:#6F008A">NULL</span><span style="font-size:9.5pt;font-family:Consolas;color:black">,
</span><span style="font-size:9.5pt;font-family:Consolas;color:#6F008A">NULL</span><span style="font-size:9.5pt;font-family:Consolas;color:black">);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:blue">if</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> (!P2G)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:blue">return</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> result;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="font-size:9.5pt;font-family:Consolas;color:gray">c_out_glob</span><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:teal">=</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> proj_trans(P2G,
</span><span style="font-size:9.5pt;font-family:Consolas;color:darkslategray">PJ_FWD</span><span style="font-size:9.5pt;font-family:Consolas;color:black">,
</span><span style="font-size:9.5pt;font-family:Consolas;color:gray">c_in</span><span style="font-size:9.5pt;font-family:Consolas;color:black">);</span><span style="mso-ligatures:none;mso-fareast-language:EN-IN"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="mso-ligatures:none;mso-fareast-language:EN-IN"><o:p> </o:p></span></p>
<ol style="margin-top:0cm" start="2" type="1">
<li class="MsoListParagraph" style="color:black;margin-left:0cm;mso-list:l1 level1 lfo2;text-autospace:none">
<span style="color:windowtext;mso-ligatures:none;mso-fareast-language:EN-IN">Are there any specific parameters or options that I need to consider while performing the projection from 3d to 2d? In the below code, I am performing projection of a point from wgs84
to oblique merctor. But still I am getting incorrect values.<br>
<br>
</span><span style="font-size:9.5pt;font-family:Consolas;color:#2B91AF">PJ</span><span style="font-size:9.5pt;font-family:Consolas"> *Src = proj_create(C,
</span><span style="font-size:9.5pt;font-family:Consolas;color:#A31515">"+proj=geocent +datum=WGS84 +type=crs"</span><span style="font-size:9.5pt;font-family:Consolas">);<o:p></o:p></span></li></ol>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:blue">if</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> (Src ==
</span><span style="font-size:9.5pt;font-family:Consolas;color:#6F008A">NULL</span><span style="font-size:9.5pt;font-family:Consolas;color:black">)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:blue">return</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> result;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:#2B91AF">PJ</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> *Targ = proj_create(C,
</span><span style="font-size:9.5pt;font-family:Consolas;color:#A31515">"+proj=omerc +lat_0=4 +lonc =115 +k_0=1 +x_0=2000000 +y_0=5000000 +lat_ts=0 +h_0=0 +alpha=53.31581 +gamma=53.130102 +lat_ts=0 +units=m +ellps=WGS84 +type=crs"</span><span style="font-size:9.5pt;font-family:Consolas;color:black">);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:blue">if</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> (Targ ==
</span><span style="font-size:9.5pt;font-family:Consolas;color:#6F008A">NULL</span><span style="font-size:9.5pt;font-family:Consolas;color:black">)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:blue">return</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> result;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:blue">auto</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> G2P = proj_create_crs_to_crs_from_pj(C, Src, Targ,
</span><span style="font-size:9.5pt;font-family:Consolas;color:#6F008A">NULL</span><span style="font-size:9.5pt;font-family:Consolas;color:black">,
</span><span style="font-size:9.5pt;font-family:Consolas;color:#6F008A">NULL</span><span style="font-size:9.5pt;font-family:Consolas;color:black">);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:blue">if</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> (!G2P)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black"> {<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black"> fprintf(</span><span style="font-size:9.5pt;font-family:Consolas;color:#6F008A">stderr</span><span style="font-size:9.5pt;font-family:Consolas;color:black">,
</span><span style="font-size:9.5pt;font-family:Consolas;color:#A31515">"failed \n"</span><span style="font-size:9.5pt;font-family:Consolas;color:black">);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:blue">return</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> result;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black"> }<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black">
<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:#2B91AF">PJ</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> *norm = proj_normalize_for_visualization(C, G2P);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:blue">if</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> (0 == norm) {<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black"> fprintf(</span><span style="font-size:9.5pt;font-family:Consolas;color:#6F008A">stderr</span><span style="font-size:9.5pt;font-family:Consolas;color:black">,
</span><span style="font-size:9.5pt;font-family:Consolas;color:#A31515">"Failed to normalize transformation object.\n"</span><span style="font-size:9.5pt;font-family:Consolas;color:black">);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:blue">return</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> 1;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black"> }<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black"> proj_destroy(G2P);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black"> G2P = norm;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="font-size:9.5pt;font-family:Consolas;color:gray">c_out</span><span style="font-size:9.5pt;font-family:Consolas;color:black">
</span><span style="font-size:9.5pt;font-family:Consolas;color:teal">=</span><span style="font-size:9.5pt;font-family:Consolas;color:black"> proj_trans(G2P,
</span><span style="font-size:9.5pt;font-family:Consolas;color:darkslategray">PJ_FWD</span><span style="font-size:9.5pt;font-family:Consolas;color:black">,
</span><span style="font-size:9.5pt;font-family:Consolas;color:gray">c_in</span><span style="font-size:9.5pt;font-family:Consolas;color:black">);</span><span style="mso-ligatures:none;mso-fareast-language:EN-IN"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:15.0pt"><span style="mso-ligatures:none;mso-fareast-language:EN-IN">Any code examples, documentation references, or step-by-step instructions you could provide would be immensely helpful in guiding
me through this process. I am eager to learn and explore the capabilities of the Proj library, and any assistance you can offer would be invaluable.<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:15.0pt"><span style="mso-ligatures:none;mso-fareast-language:EN-IN">Thank you very much for your time and support. I look forward to hearing from you soon.<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D;mso-ligatures:none;mso-fareast-language:EN-IN">Best Regards,</span><span lang="EN-US" style="mso-ligatures:none;mso-fareast-language:EN-IN"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D;mso-ligatures:none;mso-fareast-language:EN-IN">Rohith Narayandas</span><span lang="EN-US" style="mso-ligatures:none;mso-fareast-language:EN-IN"><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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