<s>
A	O
thematic	B-Application
map	I-Application
is	O
a	O
type	O
of	O
map	O
that	O
portrays	O
the	O
geographic	O
pattern	O
of	O
a	O
particular	O
subject	O
matter	O
(	O
theme	O
)	O
in	O
a	O
geographic	O
area	O
.	O
</s>
<s>
Alternative	O
names	O
have	O
been	O
suggested	O
for	O
this	O
class	O
,	O
such	O
as	O
special-subject	O
or	O
special-purpose	O
maps	O
,	O
statistical	O
maps	O
,	O
or	O
distribution	B-Application
maps	I-Application
,	O
but	O
these	O
have	O
generally	O
fallen	O
out	O
of	O
common	O
usage	O
.	O
</s>
<s>
Several	O
types	O
of	O
thematic	B-Application
maps	I-Application
have	O
been	O
invented	O
,	O
starting	O
in	O
the	O
18th	O
and	O
19th	O
centuries	O
,	O
as	O
large	O
amounts	O
of	O
statistical	O
data	O
began	O
to	O
be	O
collected	O
and	O
published	O
,	O
such	O
as	O
national	O
censuses	O
.	O
</s>
<s>
According	O
to	O
Arthur	O
Robinson	O
,	O
thematic	B-Application
maps	I-Application
were	O
largely	O
an	O
Industrial	O
Age	O
innovation	O
,	O
with	O
some	O
Enlightenment-era	O
roots	O
;	O
almost	O
all	O
of	O
the	O
modern	O
graphical	O
techniques	O
were	O
invented	O
between	O
1700	O
and	O
1850	O
.	O
</s>
<s>
Their	O
accuracy	O
improved	O
slowly	O
,	O
and	O
even	O
in	O
the	O
mid-17th	O
century	O
,	O
they	O
were	O
usually	O
of	O
poor	O
quality	O
;	O
but	O
they	O
were	O
good	O
enough	O
to	O
display	O
basic	O
information	O
,	O
allowing	O
the	O
production	O
of	O
the	O
first	O
thematic	B-Application
maps	I-Application
.	O
</s>
<s>
One	O
of	O
the	O
earliest	O
thematic	B-Application
maps	I-Application
was	O
one	O
entitled	O
Designatio	O
orbis	O
christiani	O
(	O
1607	O
)	O
by	O
Jodocus	O
Hondius	O
,	O
showing	O
the	O
dispersion	O
of	O
major	O
religions	O
using	O
map	O
symbols	O
,	O
in	O
the	O
French	O
edition	O
of	O
his	O
Atlas	O
Minor	O
(	O
1607	O
)	O
.	O
</s>
<s>
An	O
early	O
contributor	O
to	O
thematic	O
mapping	O
in	O
England	O
was	O
the	O
English	O
astronomer	O
Edmond	O
Halley	O
(	O
1656	O
–	O
1742	O
)	O
,	O
who	O
introduced	O
the	O
Enlightenment	O
conception	O
of	O
the	O
thematic	B-Application
map	I-Application
as	O
a	O
tool	O
for	O
scientific	O
thinking	O
.	O
</s>
<s>
Included	O
were	O
early	O
chorochromatic	O
and	O
flow	B-Application
maps	I-Application
,	O
and	O
possibly	O
the	O
first	O
proportional	O
point	O
symbol	O
and	O
dasymetric	O
maps	O
.	O
</s>
<s>
Though	O
disease	O
had	O
been	O
mapped	O
thematically	O
,	O
Snow	O
's	O
cholera	O
map	O
in	O
1854	O
is	O
the	O
best-known	O
example	O
of	O
using	O
thematic	B-Application
maps	I-Application
for	O
analysis	O
.	O
</s>
<s>
Essentially	O
,	O
his	O
technique	O
and	O
methodology	O
anticipated	O
the	O
principles	O
of	O
a	O
geographic	B-Application
information	I-Application
system	I-Application
(	O
GIS	B-Application
)	O
.	O
</s>
<s>
Charles	O
Joseph	O
Minard	O
has	O
been	O
hailed	O
as	O
perhaps	O
the	O
first	O
master	O
of	O
thematic	O
mapping	O
and	O
information	B-Application
visualization	I-Application
.	O
</s>
<s>
In	O
the	O
1850s	O
and	O
1860s	O
,	O
he	O
integrated	O
thematic	B-Application
maps	I-Application
(	O
especially	O
flow	B-Application
maps	I-Application
)	O
with	O
statistical	O
charts	O
to	O
create	O
visual	O
narratives	O
,	O
most	O
notably	O
his	O
1869	O
map	O
of	O
Napoleon	O
's	O
1812	O
invasion	O
of	O
Europe	O
.	O
</s>
<s>
By	O
the	O
early	O
20th	O
century	O
,	O
established	O
methods	O
were	O
in	O
place	O
for	O
manually	O
drafting	O
a	O
variety	O
of	O
thematic	B-Application
maps	I-Application
,	O
but	O
they	O
were	O
still	O
produced	O
in	O
far	O
fewer	O
numbers	O
than	O
general	O
reference	O
maps	O
,	O
and	O
occupied	O
a	O
relatively	O
small	O
portion	O
of	O
cartographic	O
education	O
.	O
</s>
<s>
Their	O
popularity	O
vastly	O
increased	O
in	O
the	O
second	O
half	O
of	O
the	O
century	O
,	O
due	O
to	O
several	O
influences	O
:	O
first	O
,	O
the	O
Quantitative	O
revolution	O
in	O
geography	O
and	O
the	O
rise	O
of	O
cartography	O
as	O
an	O
academic	O
discipline	O
,	O
both	O
of	O
which	O
increased	O
the	O
role	O
of	O
thematic	B-Application
maps	I-Application
as	O
tools	O
for	O
scientific	O
analysis	O
and	O
communication	O
;	O
second	O
,	O
technology	O
that	O
facilitates	O
map	O
design	O
and	O
production	O
,	O
especially	O
the	O
personal	B-Device
computer	I-Device
,	O
the	O
geographic	B-Application
information	I-Application
system	I-Application
(	O
GIS	B-Application
)	O
,	O
graphics	B-Application
software	I-Application
,	O
and	O
the	O
Internet	O
;	O
and	O
third	O
,	O
the	O
widespread	O
availability	O
of	O
large	O
volumes	O
of	O
data	O
,	O
notably	O
the	O
first	O
digital	O
releases	O
of	O
national	O
censuses	O
in	O
the	O
1990s	O
.	O
</s>
<s>
The	O
most	O
common	O
purpose	O
of	O
a	O
thematic	B-Application
map	I-Application
is	O
to	O
portray	O
the	O
geographic	O
distribution	O
of	O
one	O
or	O
more	O
phenomena	O
.	O
</s>
<s>
Thematic	B-Application
maps	I-Application
accomplish	O
these	O
two	O
goals	O
by	O
leveraging	O
the	O
natural	O
ability	O
of	O
the	O
human	O
visual	O
perception	O
system	O
to	O
recognize	O
patterns	O
in	O
a	O
complex	O
visual	O
field	O
,	O
which	O
is	O
necessary	O
for	O
common	O
tasks	O
such	O
as	O
object	O
recognition	O
.	O
</s>
<s>
A	O
thematic	B-Application
map	I-Application
usually	O
focuses	O
on	O
visualizing	O
the	O
distribution	O
of	O
values	O
of	O
a	O
single	O
property	O
or	O
type	O
of	O
feature	O
(	O
a	O
univariate	O
map	O
)	O
,	O
occasionally	O
including	O
two	O
(	O
bivariate	O
)	O
or	O
more	O
(	O
multivariate	O
)	O
properties	O
or	O
feature	O
types	O
that	O
are	O
hypothesized	O
to	O
be	O
statistically	O
correlated	O
or	O
otherwise	O
closely	O
related	O
.	O
</s>
<s>
By	O
focusing	O
on	O
a	O
single	O
subject	O
matter	O
,	O
the	O
thematic	B-Application
map	I-Application
is	O
typically	O
intended	O
to	O
be	O
used	O
for	O
a	O
narrower	O
range	O
of	O
tasks	O
than	O
a	O
reference	O
map	O
.	O
</s>
<s>
Cartographers	O
use	O
many	O
methods	O
to	O
create	O
thematic	B-Application
maps	I-Application
.	O
</s>
<s>
These	O
are	O
often	O
referred	O
to	O
as	O
different	O
types	O
of	O
thematic	B-Application
maps	I-Application
,	O
but	O
it	O
is	O
more	O
proper	O
to	O
call	O
them	O
types	O
of	O
thematic	B-Application
map	I-Application
layers	O
or	O
thematic	O
mapping	O
techniques	O
,	O
as	O
they	O
can	O
be	O
combined	O
with	O
each	O
other	O
(	O
forming	O
a	O
bivariate	O
or	O
multivariate	O
map	O
)	O
and	O
with	O
one	O
or	O
more	O
reference	O
map	O
layers	O
in	O
a	O
single	O
map	O
.	O
</s>
<s>
Visual	O
variables	O
filling	O
each	O
region	O
are	O
used	O
to	O
represent	O
each	O
aggregate	O
summary	O
value	O
:	O
hue	B-Language
is	O
commonly	O
used	O
for	O
qualitative	O
variables	O
,	O
such	O
as	O
predominant	O
land	O
use	O
,	O
while	O
lightness	O
is	O
most	O
common	O
for	O
quantitative	O
differences	O
,	O
such	O
as	O
population	O
density	O
.	O
</s>
<s>
This	O
technique	O
is	O
very	O
popular	O
due	O
to	O
the	O
widespread	O
availability	O
of	O
such	O
aggregate	O
statistical	O
data	O
as	O
well	O
as	O
GIS	B-Application
data	O
for	O
common	O
regions	O
,	O
but	O
the	O
loss	O
of	O
information	O
inherent	O
in	O
aggregate	O
information	O
can	O
result	O
in	O
interpretation	O
issues	O
such	O
as	O
the	O
Ecological	O
fallacy	O
and	O
the	O
Modifiable	O
areal	O
unit	O
problem	O
.	O
</s>
<s>
A	O
chorochromatic	O
or	O
area-class	O
map	O
represents	O
a	O
categorical	O
or	O
nominal	O
variable	O
distributed	O
over	O
space	O
(	O
also	O
known	O
as	O
a	O
discrete	O
field	O
)	O
,	O
by	O
using	O
different	O
area	O
symbols	O
(	O
usually	O
color	O
hue	B-Language
)	O
to	O
represent	O
regions	O
of	O
homogeneous	O
value	O
.	O
</s>
<s>
A	O
dot	O
distribution	B-Application
map	I-Application
places	O
small	O
point	O
symbols	O
over	O
a	O
given	O
space	O
to	O
indicate	O
the	O
distribution	O
of	O
a	O
given	O
phenomenon	O
.	O
</s>
<s>
Flow	B-Application
maps	I-Application
are	O
maps	O
that	O
use	O
line	O
symbols	O
to	O
portray	O
movement	O
or	O
relationship	O
between	O
two	O
or	O
more	O
places	O
,	O
such	O
as	O
air	O
travel	O
,	O
monetary	O
aid	O
,	O
or	O
economic	O
trade	O
.	O
</s>
<s>
Some	O
flow	B-Application
maps	I-Application
simply	O
show	O
the	O
presence	O
of	O
connections	O
,	O
while	O
others	O
use	O
visual	O
variables	O
such	O
as	O
size	O
(	O
width	O
)	O
or	O
color	O
to	O
represent	O
the	O
properties	O
of	O
each	O
connection	O
.	O
</s>
<s>
While	O
the	O
thematic	O
information	O
is	O
the	O
core	O
of	O
a	O
thematic	B-Application
map	I-Application
,	O
other	O
geographic	O
features	O
may	O
also	O
be	O
included	O
as	O
reference	O
information	O
.	O
</s>
