<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>use the proj geod utility</div><div><br></div><div><a href="http://trac.osgeo.org/proj/wiki/man_geod">http://trac.osgeo.org/proj/wiki/man_geod</a></div><div><br></div><div><br></div>or NGS has an online calculator that you can test some points with<div><br></div><div><a href="http://www.ngs.noaa.gov/cgi-bin/Inv_Fwd/inverse2.prl">http://www.ngs.noaa.gov/cgi-bin/Inv_Fwd/inverse2.prl</a></div><div><br></div><div> Norman</div><div><br><div><div>On Oct 1, 2010, at 12:14 PM, Robert McFaul wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div>Hi,<br><br>I'm concerned about whether ground surface distances are different between<br>NAD27 and NAD83. I'm in California (southern) and thinking about a <br>conversion<br>of a project to NAD83. I have some cross section distances measured (1000 to<br>3000 feet in length) and suddenly am wondering what sort of differences <br>might<br>be involved by this change in systems.<br><br>What can I expect here?<br><br>Thanks.<br><br>robert mcfaul<br><a href="mailto:robert@dgi.com">robert@dgi.com</a><br><br><br><br>_______________________________________________<br>Proj mailing list<br>Proj@lists.maptools.org<br>http://lists.maptools.org/mailman/listinfo/proj<br></div></blockquote></div><br></div></body></html>