/*
 * Object distance calculations.
 * By Dave Pearson <davep@davep.org>
 */

function doDistCalc()
{
   var diameter  = document.getElementById( "distDiameter" ).options[ document.getElementById( "distDiameter" ).selectedIndex ].value;
   var result    = document.getElementById( "distResult" );
   var size      = document.getElementById( "angSize" ).value;
   var angType   = document.getElementById( "angType" ).options[ document.getElementById( "angType" ).selectedIndex ].value;

   // Sort out the desired size.
   switch ( angType )
   {
      case "1" : size = size / 60; break;
      case "2" : size = size / ( 60 * 60 ); break;
   }

   // Calculate it.
   result.innerHTML =
      "Approximate distance would need to be " +
      StringifyFloat( ( diameter / 2 ) *
                      Math.sqrt( 1 / ( 1 - ( Math.cos( degToRad( size ) / 2 ) *
                                             Math.cos( degToRad( size ) / 2 ) ) ) ),
                      2 ) + " km";
}