<s>
Turn-by-turn	B-Application
navigation	I-Application
is	O
a	O
feature	O
of	O
some	O
satellite	O
navigation	O
devices	O
where	O
directions	O
for	O
a	O
selected	O
route	O
are	O
continually	O
presented	O
to	O
the	O
user	O
in	O
the	O
form	O
of	O
spoken	O
or	O
visual	O
instructions	O
.	O
</s>
<s>
Mathematically	O
,	O
turn	B-Application
by	I-Application
turn	I-Application
navigation	I-Application
is	O
based	O
on	O
the	O
shortest	O
path	O
problem	O
within	O
graph	O
theory	O
,	O
which	O
examines	O
how	O
to	O
identify	O
the	O
path	O
that	O
best	O
meets	O
some	O
criteria	O
(	O
shortest	O
,	O
cheapest	O
,	O
fastest	O
,	O
etc	O
.	O
)	O
</s>
<s>
Real-time	O
turn-by-turn	B-Application
navigation	I-Application
instructions	O
by	O
computer	O
was	O
first	O
developed	O
at	O
the	O
MIT	O
Media	O
Laboratory	O
by	O
James	O
Raymond	O
Davis	O
and	O
Christopher	O
M	O
.	O
Schmandt	O
in	O
1988	O
.	O
</s>
<s>
Major	O
mapping	O
services	O
that	O
offer	O
turn-by-turn	B-Application
navigation	I-Application
,	O
grouped	O
by	O
map	O
data	O
provider	O
:	O
</s>
<s>
HERE	B-Application
Technologies	I-Application
:	O
</s>
<s>
Google	B-Application
:	O
</s>
