< "Triangulated Irregular Network", or TIN:
That is the ne name of the result of the inside Sketchup Tool "SandBox" / Make by contour = Tin surface ;)

2 very good tutorial video (just wait seconds to start loading it's QuickTime )
http://go-2-school.com/media/view/41 use of the SandBox
http://go-2-school.com/media/view/37 for 4 methods of building terrain with the sandbox

and if you will use Sketchup and import cadastral's files don't forget to use the plug "Simplify contour"
the last of the page
http://sketchup.google.com/intl/en/download/rubyscripts.html