The universal model SC is coordinates and binary relations between
pairs of coordinates. This is purely an edge (or segment) model, with all
higher level structures recorded as groupings of edges.
SC(x, ...)
# Default S3 method
SC(x, ...)
# S3 method for class 'TRI'
SC(x, ...)
# S3 method for class 'pslg'
SC(x, ...)SC model with tables 'object', 'object_link_edge', 'edge', and 'vertex'