Each line segment in X will be subdivided into equal pieces.
  The result is an object of the same kind as X, representing the
  same data as X except that the segments have been subdivided.
Splitting is controlled by the arguments nsplit and eps,
  exactly one of which should be given.
If nsplit is given, it specifies the 
  number of pieces into which each line segment of X
  should be divided. It should be either a single integer, or an integer vector
  of length equal to the number of line segments in X.
If eps is given, it specifies the maximum length of
  any resulting piece of line segment.
It is strongly advisable to use sparse=TRUE (the default)
  to limit the computation time.
If X is a point pattern (class "lpp") then the
  spatial coordinates and marks of each data point are unchanged, but the
  local coordinates will change, because they are
  adjusted to map them to the new subdivided network.