trip by
exact cell crossing methods, weighted by the time between locations
for separate trip events.tripGrid(x, grid = NULL, method = "pixellate", ...)tripGrid returns an object of class SpatialGridDataFrame, with one
column "z" containing the time spent in each cell in seconds.pixellate.psp and pixellate.ppp for the details on
the method used. See density.psp for method = "density".
Trip events are assumed to start and end as per the object passed
in. To work with inferred "cutoff" positions see
split.trip.exact.