ground overlap

[wbs]

Dear all,
I import 3d buildings from SketchUp to vizard, the ground is overlapped. But if i delete the ground = viz.addchild code, it's black and can not show the roads, grass in the SketchUp. How can I solve this problem? thanks.

import viz
import vizact
import vizcam
import webbrowser
viz.setMultiSample(4)
viz.fov(60)
viz.go()
strijp=viz.addChild('srtijp-s building.osgb')
viz.MainView.move([0,100,-3])
viz.collision(viz.ON)
keyCam = vizcam.KeyboardCamera()
gound=viz.addChild('ground.osgb')
ground.collidePlane()

text=viz.addText3D('strijp-s',pos=[-10,5,-6])
def pickobject():
obj=viz.pick()
if obj==text:
webbrowser.open('file:///C:/Netherlands/system%20create/Website%20-wang/index.html')
vizact.onmousedown(viz.MOUSEBUTTON_LEFT,pickobject )
mySound=viz.addAudio('introduction of strijp-s.mp3')
vizact.onkeydown('p',mySound.play)
vizact.onkeydown('o',mySound.stop)