<s>
A	O
historical	B-Application
geographic	I-Application
information	I-Application
system	I-Application
(	O
also	O
written	O
as	O
historical	B-Application
GIS	I-Application
or	O
HGIS	B-Application
)	O
is	O
a	O
geographic	B-Application
information	I-Application
system	I-Application
that	O
may	O
display	O
,	O
store	O
and	O
analyze	O
data	O
of	O
past	O
geographies	O
and	O
track	O
changes	O
in	O
time	O
.	O
</s>
<s>
Digitization	O
and	O
georeferencing	B-General_Concept
of	O
historical	O
maps	O
:	O
Old	O
maps	O
may	O
contain	O
valuable	O
information	O
about	O
the	O
past	O
.	O
</s>
<s>
By	O
adding	O
coordinates	O
to	O
such	O
maps	O
,	O
they	O
may	O
be	O
added	O
as	O
a	O
feature	O
layer	O
to	O
modern	O
GIS	B-Application
data	O
:	O
This	O
facilitates	O
comparison	O
of	O
different	O
map	O
layers	O
showing	O
the	O
geography	O
at	O
different	O
times	O
.	O
</s>
<s>
The	O
maps	O
may	O
be	O
further	O
enhanced	O
by	O
techniques	O
such	O
as	O
rubbersheeting	B-Application
,	O
which	O
spatially	O
warps	O
the	O
data	O
to	O
fit	O
with	O
more	O
accurate	O
modern	O
maps	O
.	O
</s>
<s>
Reconstruction	O
of	O
past	O
boundaries	O
:	O
By	O
creating	O
polygons	B-General_Concept
of	O
former	O
political	O
entities	O
,	O
administrative	O
sub-divisions	O
and	O
other	O
types	O
of	O
borders	O
,	O
their	O
evolution	O
as	O
well	O
as	O
aggregated	O
statistics	O
can	O
be	O
compared	O
through	O
time	O
.	O
</s>
<s>
Georeferencing	B-General_Concept
of	O
historical	O
microdata	O
(	O
such	O
as	O
census	O
or	O
parish	O
records	O
)	O
:	O
This	O
enables	O
the	O
use	O
of	O
spatial	O
analysis	O
to	O
historical	O
data	O
.	O
</s>
<s>
China	O
Historical	B-Application
GIS	I-Application
is	O
a	O
project	O
on	O
Imperial	O
China	O
developed	O
by	O
Harvard	O
University	O
and	O
Fudan	O
University	O
.	O
</s>
<s>
Electronic	O
Cultural	O
Atlas	O
Initiative	O
(	O
ECAI	O
)	O
is	O
a	O
clearinghouse	O
for	O
the	O
exchange	O
of	O
metadata	O
of	O
Historical	B-Application
GIS	I-Application
.	O
</s>
<s>
Great	O
Britain	O
Historical	B-Application
GIS	I-Application
is	O
a	O
GIS-enabled	O
database	O
holding	O
diverse	O
geo-referenced	B-General_Concept
maps	O
,	O
statistics	O
,	O
gazetteers	O
and	O
travel	O
writing	O
,	O
especially	O
for	O
the	O
period	O
1801	O
–	O
2001	O
covered	O
by	O
British	O
censuses	O
.	O
</s>
<s>
HistoAtlas	B-Application
is	O
an	O
open	O
historical	B-Application
geographical	I-Application
information	I-Application
system	I-Application
that	O
tries	O
to	O
build	O
a	O
free	O
historical	O
atlas	O
of	O
the	O
world	O
.	O
</s>
<s>
National	O
Historical	B-Application
Geographic	I-Application
Information	I-Application
System	I-Application
(	O
NHGIS	O
)	O
is	O
a	O
system	O
for	O
displaying	O
and	O
analyzing	O
Census	O
tracts	O
and	O
tract	O
changes	O
in	O
the	O
United	O
States	O
.	O
</s>
<s>
Google	B-Application
Earth	I-Application
added	O
a	O
time	O
line	O
feature	O
in	O
version	O
4	O
(	O
2006	O
)	O
that	O
enables	O
simple	O
temporal	O
browsing	O
of	O
spatial	O
data	O
.	O
</s>
<s>
TimeMap	B-Application
is	O
a	O
Java	B-Language
open-source	O
applet	O
(	O
or	O
program	O
)	O
for	O
browsing	O
spatial-temporal	O
data	O
and	O
ECAI	O
data	O
sets	O
.	O
</s>
