<div dir="ltr"><div><div><div><div><div><div>Hi<br></div>That program provides the rotation matrix and not the angles, but you can easily convert them from radians to arcseconds, to use in string +towgs84. Check the formulas in page 134 of document <a href="http://www.epsg.org/Portals/0/373-07-2.pdf" target="_blank">http://www.epsg.org/Portals/0/<wbr>373-07-2.pdf.</a> PROJ.4 uses the Position Vector" standard.</div><div>You can get the angles from matrix elements:<br></div><div>Rz = -r12 * 3600 *180 / PI</div><div>Ry = r13 * 3600 * 180 / PI</div><div>Rx = -r23 * 3600 * 180 / PI</div><div><br></div><div>The scale factor must be converted to scale difference in ppm: <br></div><div>DS = (s-1) * 1000000</div><div><br></div><div>You don't need to change translation vector components.<br></div><div><br></div>Regards</div><div><br></div><div>José Gonçalves<br></div></div></div></div><br></div><div class="gmail_extra"><br><div class="gmail_quote">2017-09-25 13:16 GMT+01:00 Mark Johnson <span dir="ltr"><<a href="mailto:mj10777@googlemail.com" target="_blank">mj10777@googlemail.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Is there a c program source that can take a list of x/y/z points for a source and destination and calculate a valid 7 parameter +towgs84 value that could be used with cs2cs?<div><br></div><div>I found something similar at <a href="http://helmparms3d.sourceforge.net/" target="_blank">http://helmparms3d.<wbr>sourceforge.net/</a>, called helmparms3d - but it seems calculate values that cannot be used for +towgs84.<br><div><br></div><div>Mark Johnson, Berlin Germany</div></div></div>
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