[postgis-users] Intersection Problem

[caij at lreis.ac.cn]

Hi all,
    I came across a wield problem today when I use the Intersection function to get the intersection line of two neighbor polygons which are 3D.
    And I found that the z-value of the result is the average of two the points',such as one z-value is 0 and the other is 1,the result is 0.5.But some will turn to be zero when One is 1 and the other is 0.I don't know why.
    Does anyone else come across the same problem?And who knows the way to solve the problem?
    Expect for ur answers.