If you haul around the tape and make stakes you can also effectively make use of the small angle equation:<br>http://ceres.hsc.edu/homepages/classes/astronomy/spring99/Mathematics/sec7.html<br><br>http://www.astro.washington.edu/astro211/smanAA/smangleA.html<br><br>http://dilbert.physast.uga.edu/~derek/ASTR1020/numbers.html<br><br>Of course, if you happen to have a topo map and can determine a height then you can accurately compute the distance...