<html><body><div style="color:#000; background-color:#fff; font-family:arial, helvetica, sans-serif;font-size:12pt"><div><span>Quick question- <br></span></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;"><span><br></span></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;"><span>having had a very similar discussion on the Postgis list regarding ST_Project()<br></span></div><div>does geod propagate a straight line at constant bearing, or a great circle arc, to locate the new point?</div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent;
font-style: normal;">looking at these examples (the first gives a slightly different return azimuth to Frank's example for some reason):</div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;"> <br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;">echo "33 -117 15 10000" | geod +ellps=WGS84<br>33d5'12.363"N 116d58'20.1"W -164d59'5.527"<br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;">echo "33 -117 90 10000" | geod +ellps=WGS84<br>32d59'59.835"N
116d53'34.398"W -89d56'29.986"<br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;">echo "33 -117 90 1000000" | geod +ellps=WGS84<br>32d32'41.22"N 106d19'31.529"W -84d12'35.763"<br><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;">given the changes in return azimuth & latitude I'm assuming the azimuth given on the command line is not the constant bearing to the point, but the start bearing of a great circle arc crossing that point.<br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color:
transparent; font-style: normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;">Thanks</div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;"> Brent Wood<br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style:
normal;"><br></div> <div style="font-family: arial, helvetica, sans-serif; font-size: 12pt;"> <div style="font-family: times new roman, new york, times, serif; font-size: 12pt;"> <div dir="ltr"> <hr size="1"> <font face="Arial" size="2"> <b><span style="font-weight:bold;">From:</span></b> Frank Warmerdam <warmerdam@pobox.com><br> <b><span style="font-weight: bold;">To:</span></b> PROJ.4 and general Projections Discussions <proj@lists.maptools.org> <br> <b><span style="font-weight: bold;">Sent:</span></b> Tuesday, December 17, 2013 11:16 AM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [Proj] (no subject)<br> </font> </div> <div class="y_msg_container"><br><div id="yiv7753034907"><div dir="ltr">Siva, <div><br></div><div>I believe you want to use the "geod" program distributed with PROJ.4. The man page, possibly a bit out of date is at:</div><div><br></div><div> <a rel="nofollow" target="_blank"
href="http://trac.osgeo.org/proj/wiki/man_geod">http://trac.osgeo.org/proj/wiki/man_geod</a></div>
<div><br></div><div>Example use:</div><div><div>$ geod +ellps=WGS84</div><div><br></div><div>Input:</div><div>33 -117 15 10000</div><div><br></div><div>Output:</div><div>33d5'13.53"N<span class="yiv7753034907" style="white-space:pre;"> </span>116d58'20.2"W<span class="yiv7753034907" style="white-space:pre;"> </span>-164d59'5.581"</div>
</div><div><br></div><div>So if you gave it an initial location of 33N 117W, an azimuth(bearing) of 15 degrees and a distance 10000m you would arrive at the output location given with the third value being the azimuth back to the original point. </div>
<div><br></div><div>You should be able to construct what you want from this.</div><div><br></div><div>There is also a corresponding C API.</div><div><br></div><div>Best regards,</div><div>Frank</div><div><br></div><div><br>
</div></div><div class="yiv7753034907gmail_extra"><br><br><div class="yiv7753034907gmail_quote">On Sun, Dec 15, 2013 at 10:56 PM, SIVA RAMA KRISHNA <span dir="ltr"><<a rel="nofollow" ymailto="mailto:s.r.kriishna@gmail.com" target="_blank" href="mailto:s.r.kriishna@gmail.com">s.r.kriishna@gmail.com</a>></span> wrote:<br>
<blockquote class="yiv7753034907gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div dir="ltr"><div><div>Hello,<br><br></div><div>Thanks in advance<br></div><div><br></div>I have a <b>lat, lon</b> coordinate with a known projection system I assume it a initial point. I want to generate a next Position with the an <br>
<br><b>angle</b> with (horizontal/vertical) and <b>bearing length</b> in lat,lon coordinates and complete it with angles and bearing lengths to form a<br><br></div><div>polygon<br><br><br></div><div>Any Help in the above context is highly appreciated<br>
</div></div>
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