When transmitting an on-road location on a digital map, an information
provider transmits, as on-road location information, string of
coordinates information representing the road shape of a road section
including the on-road location having a predetermined length, additional
information including at least one information item chosen from a group
of the attribute information on the road including the road location and
detailed information on the nodes in the road section, and relative
information indicating the on-road location in the road section.
Receiving party receiving this on-road location information performs
shape matching to identify the road section on a digital map and uses
relative data to identify the on-road location in this road section. The
receiving party can identify the road shape with high accuracy even when
only a small amount of string of coordinates data is available. This
makes it possible to reduce the data transmission amount and identify an
on-load location with high accuracy.