Originally Posted by
nguyenhoangquan
Another reason can be settings of the surface build (definition tag in surface properties). When you add feature lines into a surface, whenever a crossing or overlapping of feature lines occur - a solution is needed. 4 options are available:
1. Will not alow the added feature lines/ breaklines
2. Use elevation of lastly added feature line(s)
3. Use elevations of first added feature line(s)
4. Use average elevations of feature lines at crossing
In your case, it can be option 3 or option 4 was selected that causes changes in elevations/grades of your feature lines. Also, within one SITE there will be only 1 elevation at one location thus there will be mutual influence between feature lines crossing each other.