I am converting XY coordinates to SN coordinates (orthogonal curvilinear coordinates) for points within a stream. The purpose is basically to straighten out the stream to take into account the linear nature. One end of the riverline is set as S=0, N=0. S increases with the length of the river centerline. N increases with distance from the centerline. N values are positive on the right side of the line and negative on the left side. I could highlight all points on the right or left side to manually assign these .... but I have thousands of points. Is there a way to automate the assignment for whether the points are on the right or left side of a centerline?