I have 3 shapefiles that I want to use to create a perpendicular polyline from. First I have my river polyline, then about 2000 random points along the river line, and finally the riparian area polygon. I need to create a line (a sampling transect) perpendicular to the river polyline that is within (or clipped to) the riparian area boundary. Has anyone ever done anything similar? Or know how to do it simply?