<s>
In	O
computer	O
graphics	O
,	O
a	O
triangulated	B-Algorithm
irregular	I-Algorithm
network	I-Algorithm
(	O
TIN	O
)	O
is	O
a	O
representation	O
of	O
a	O
continuous	O
surface	O
consisting	O
entirely	O
of	O
triangular	O
facets	O
(	O
a	O
triangle	B-Algorithm
mesh	I-Algorithm
)	O
,	O
used	O
mainly	O
as	O
Discrete	O
Global	O
Grid	O
in	O
primary	O
elevation	O
modeling	O
.	O
</s>
<s>
The	O
vertices	O
of	O
these	O
triangles	O
are	O
created	O
from	O
field	O
recorded	O
spot	O
elevations	O
through	O
a	O
variety	O
of	O
means	O
including	O
surveying	O
through	O
conventional	O
techniques	O
,	O
Global	O
Positioning	O
System	O
Real-Time	O
Kinematic	O
(	O
GPS	O
RTK	O
)	O
,	O
photogrammetry	B-Application
,	O
or	O
some	O
other	O
means	O
.	O
</s>
<s>
Digital	O
TIN	O
data	B-General_Concept
structures	I-General_Concept
are	O
used	O
in	O
a	O
variety	O
of	O
applications	O
,	O
including	O
geographic	B-Application
information	I-Application
systems	I-Application
(	O
GIS	B-Application
)	O
,	O
and	O
computer	B-Application
aided	I-Application
design	I-Application
(	O
CAD	B-Application
)	O
for	O
the	O
visual	O
representation	O
of	O
a	O
topographical	O
surface	O
.	O
</s>
<s>
A	O
TIN	O
comprises	O
a	O
triangular	O
network	O
of	O
vertices	O
,	O
known	O
as	O
mass	O
points	O
,	O
with	O
associated	O
coordinates	O
in	O
three	O
dimensions	O
connected	O
by	O
edges	O
to	O
form	O
a	O
triangular	O
tessellation	B-Algorithm
.	O
</s>
<s>
A	O
TIN	O
used	O
to	O
represent	O
terrain	O
is	O
often	O
called	O
a	O
digital	B-Application
elevation	I-Application
model	I-Application
(	O
DEM	O
)	O
,	O
which	O
can	O
be	O
further	O
used	O
to	O
produce	O
digital	B-Application
surface	I-Application
models	I-Application
(	O
DSM	O
)	O
or	O
digital	B-Application
terrain	I-Application
models	I-Application
(	O
DTM	O
)	O
.	O
</s>
<s>
An	O
advantage	O
of	O
using	O
a	O
TIN	O
over	O
a	O
rasterized	O
digital	B-Application
elevation	I-Application
model	I-Application
(	O
DEM	O
)	O
in	O
mapping	O
and	O
analysis	O
is	O
that	O
the	O
points	O
of	O
a	O
TIN	O
are	O
distributed	O
variably	O
based	O
on	O
an	O
algorithm	O
that	O
determines	O
which	O
points	O
are	O
most	O
necessary	O
to	O
create	O
an	O
accurate	O
representation	O
of	O
the	O
terrain	O
.	O
</s>
<s>
While	O
a	O
TIN	O
may	O
be	O
considered	O
less	O
suited	O
than	O
a	O
raster	O
DEM	O
for	O
certain	O
kinds	O
of	O
GIS	B-Application
applications	O
,	O
such	O
as	O
analysis	O
of	O
a	O
surface	O
's	O
slope	O
and	O
aspect	O
,	O
it	O
is	O
often	O
used	O
in	O
CAD	B-Application
to	O
create	O
contour	O
lines	O
.	O
</s>
<s>
TIN	O
are	O
based	O
on	O
a	O
Delaunay	B-Algorithm
triangulation	I-Algorithm
or	O
constrained	O
Delaunay	O
.	O
</s>
<s>
A	O
constrained	O
Delaunay	B-Algorithm
triangulation	I-Algorithm
can	O
be	O
considered	O
when	O
you	O
need	O
to	O
explicitly	O
define	O
certain	O
edges	O
that	O
are	O
guaranteed	O
not	O
to	O
be	O
modified	O
(	O
that	O
is	O
,	O
split	O
into	O
multiple	O
edges	O
)	O
by	O
the	O
triangulator	O
.	O
</s>
<s>
Constrained	O
Delaunay	B-Algorithm
triangulations	I-Algorithm
are	O
also	O
useful	O
for	O
minimizing	O
the	O
size	O
of	O
a	O
TIN	O
,	O
since	O
they	O
have	O
fewer	O
nodes	O
and	O
triangles	O
where	O
breaklines	O
are	O
not	O
densified	O
.	O
</s>
<s>
The	O
first	O
triangulated	B-Algorithm
irregular	I-Algorithm
network	I-Algorithm
program	O
for	O
GIS	B-Application
was	O
written	O
by	O
W	O
.	O
Randolph	O
Franklin	O
,	O
under	O
the	O
direction	O
of	O
David	O
Douglas	O
and	O
Thomas	O
Peucker	O
(	O
Poiker	O
)	O
,	O
at	O
Simon	O
Fraser	O
University	O
in	O
1973	O
.	O
</s>
