[求助]mapbasic语言中关于等高线的函数

<P>高手指教：</P>
<P>　在等高线图层中如何判断任意一点处是否有等高线？？？？？</P>
<P>根据mapbasic里的什么函数？</P>

<P>'a: your point obj</P>
<P>'l: your line obj</P>
<P>'ltab: your line table</P>
<P>select obj from ltab where obj intersects a into temp01</P>
<P>if selectioninfo(3)=0 then</P>
<P>   'a 点处有等高线</P>
<P>else </P>
<P>  'a 点处无等高线</P>
<P>end if</P>

<P>谢谢</P>

<P><img src="images/post/smile/dvbbs/em02.gif" /><img src="images/post/smile/dvbbs/em02.gif" /><img src="images/post/smile/dvbbs/em02.gif" /><img src="images/post/smile/dvbbs/em02.gif" /><img src="images/post/smile/dvbbs/em02.gif" /></P>