[求助]帮忙看看区域图元交集并集的问题

<P>我要求图层中两个region的交集和并集的面积，代码如下：</P>
<P>var<BR>  tmpFeature , tmpFeature2 , tmpInsFeature: feature;</P>
<P>  tmps : double;</P>
<P>  ly : layer;<BR>begin</P>
<P>  tmpFeature2 := ly.AllFeatures.Item[1];<BR>  tmpFeature := ly.AllFeatures.Item[2];</P>
<P>  tmpInsFeature := map1.FeatureFactory.CombineFeatures(tmpFeature,tmpFeature2);</P>
<P>  tmps := tmpInsFeature.area;</P>
<P>  tmpInsFeature := map1.FeatureFactory.IntersectFeatures(tmpFeature,tmpFeature2);</P>
<P>  tmps :=  tmpInsFeature.area;</P>
<P>end</P>
<P>但是这样求出来的交集和并集都不对，交集的面积明显很小，而并集图元更是0点图元。</P>
<P>哪里不对了？</P>