<!-- Author: Brian Mackenzie -->
<!-- Date: 10 April 2009 -->
<!-- Version: 1.0 -->

function calculate()
{
  var alt = eval(document.windalt.alt.value);
  var winds = eval(document.windalt.winds.value);
  var t100 = eval(document.windalt.t100.value);
  d=Math.exp(-0.000125*alt);
  ta=(1.03-0.03*d*Math.pow(1.0-winds*t100/100,2))*t100;
  document.windalt.ta100.value = nt2dp(ta,2);
}

function valclear()
{
  document.windalt.ta100.value = "";
}

function nt2dp(num,dp)
{
<!-- rounds num to dp decimal places -->
  num=num*1+(0.55/Math.pow(10,dp));
  if (dp>0) dp=dp+1;
  b=Math.floor(num).toString().length+dp;
  return num.toString().substr(0,b);
}