[求助]多边形面积计算

<P>那位高手用IMS写过计算多边形面积的算法啊?</P>

<P>function ComputeArea() {<BR>  <BR>  var workarea = 0.0;</P>
<P>  cai = clickCount - 1;<BR>  caj = 0;</P>
<P><BR>  while (caj < clickCount) {<BR>    xjyi = clickPointX[caj] * clickPointY[cai];<BR>    xiyj = clickPointX[cai] * clickPointY[caj];</P>
<P>    xydiff = (xjyi - xiyj);<BR>    workarea = workarea+xydiff;</P>
<P><BR>    cai = caj;<BR>    caj = parseFloat(caj + 1);  <BR>  }<BR>  <BR>//alert(ScaleBarUnits);<BR>//alert(MapUnits);<BR>  units2 = invertUnits(ScaleBarUnits, MapUnits);<BR>//alert(units2);<BR>  units2 = units2 * units2;<BR>//alert(units2);</P>
<P>/*<BR>//workarea = Math.abs(workarea / ( 2.0 * units2) * 640);   // hard-coded for SqMiles to Acres<BR>  workarea = Math.abs(workarea / ( 2.0 * units2));    // hard-coded for SqMiles</P>
<P>  var u = Math.pow(10,numDecimals);<BR>  if (!isNav) workarea = parseInt(workarea * u + 0.5) / u<BR>  workACRES = 10*(workarea/43560);</P>
<P>  currentArea = workarea*10;<BR>*/<BR>currentArea = Math.abs(workarea / 2.0);<BR>workACRES =  currentArea / 1000000;<BR>  <BR>}</P>

多谢mytest了

<img src="images/post/smile/dvbbs/em04.gif" /><img src="images/post/smile/dvbbs/em04.gif" /><img src="images/post/smile/dvbbs/em04.gif" />