<s>
Coverages	O
play	O
an	O
important	O
role	O
in	O
geographic	B-Application
information	I-Application
systems	I-Application
(	O
GIS	B-Application
)	O
,	O
geospatial	B-General_Concept
content	O
and	O
services	O
,	O
GIS	B-General_Concept
data	I-General_Concept
processing	O
,	O
and	O
data	B-Application
sharing	I-Application
.	O
</s>
<s>
For	O
example	O
,	O
a	O
satellite	B-Application
image	O
derived	O
from	O
remote	B-Application
sensing	I-Application
might	O
record	O
varying	O
degrees	O
of	O
light	O
pollution	O
.	O
</s>
<s>
Aerial	O
photography	O
,	O
land	O
cover	O
data	O
,	O
and	O
digital	B-Application
elevation	I-Application
models	I-Application
all	O
provide	O
coverage	B-General_Concept
data	I-General_Concept
.	O
</s>
<s>
Generally	O
,	O
a	O
coverage	O
can	O
be	O
multi-dimensional	O
,	O
such	O
as	O
1-D	O
sensor	O
timeseries	O
,	O
2-D	O
satellite	B-Application
images	O
,	O
3-D	O
x/y/t	O
image	O
time	O
series	O
or	O
x/y/z	O
geo	O
tomograms	B-Algorithm
,	O
or	O
4-D	O
x/y/z/t	O
climate	O
and	O
ocean	O
data	O
.	O
</s>
<s>
An	O
interoperable	O
service	O
definition	O
for	O
navigating	O
,	O
accessing	O
,	O
processing	O
,	O
and	O
aggregation	O
of	O
coverages	O
is	O
provided	O
by	O
the	O
Open	O
Geospatial	B-General_Concept
Consortium	O
(	O
OGC	O
)	O
Web	B-Application
Coverage	I-Application
Service	I-Application
(	O
WCS	O
)	O
suite	O
and	O
Web	B-Application
Coverage	I-Application
Processing	I-Application
Service	I-Application
(	O
WCPS	O
)	O
,	O
a	O
spatio-temporal	O
coverage	O
query	O
language	O
.	O
</s>
<s>
Coverages	O
represent	O
digital	O
geospatial	B-General_Concept
information	I-General_Concept
representing	O
space/time	O
-varying	O
phenomena	O
.	O
</s>
<s>
This	O
abstract	O
coverage	O
model	O
is	O
concretized	O
to	O
the	O
level	O
of	O
interoperability	O
by	O
the	O
OGC	O
standard	O
GML	O
3.2.1	O
Application	O
Schema	O
-	O
Coverages	O
(	O
often	O
referred	O
to	O
as	O
GMLCOV	O
)	O
which	O
in	O
turn	O
is	O
based	O
on	O
the	O
Geography	O
Markup	O
Language	O
(	O
GML	O
)	O
3.2	O
,	O
an	O
XML	B-Protocol
grammar	O
written	O
in	O
XML	B-Protocol
Schema	O
for	O
the	O
description	O
of	O
application	O
schemas	O
as	O
well	O
as	O
the	O
transport	O
and	O
storage	O
of	O
geographic	B-General_Concept
information	I-General_Concept
.	O
</s>
<s>
The	O
European	O
legal	O
framework	O
for	O
a	O
unified	O
Spatial	B-General_Concept
Data	I-General_Concept
Infrastructure	O
,	O
INSPIRE	O
,	O
in	O
its	O
Annex	O
II	O
and	O
III	O
relies	O
on	O
the	O
OGC	O
definitions	O
of	O
coverages	O
as	O
well	O
,	O
but	O
modifies	O
them	O
in	O
places	O
in	O
a	O
way	O
making	O
them	O
less	O
compatible	O
and	O
interoperable	O
with	O
the	O
OGC	O
standard	O
.	O
</s>
<s>
The	O
format-independent	O
logical	O
structure	O
of	O
coverages	O
can	O
be	O
mapped	O
to	O
GML	O
(	O
such	O
as	O
for	O
sensor	O
time	O
series	O
)	O
or	O
to	O
any	O
of	O
a	O
series	O
of	O
data	O
formats	O
,	O
such	O
as	O
GeoTIFF	B-Application
,	O
NetCDF	B-Application
,	O
HDF-EOS	B-Application
,	O
or	O
NITF	O
.	O
</s>
<s>
As	O
some	O
of	O
these	O
encoding	O
formats	O
are	O
not	O
capable	O
of	O
incorporating	O
all	O
metadata	O
making	O
up	O
a	O
coverage	O
,	O
the	O
coverage	O
model	O
foresees	O
a	O
multipart	O
MIME	B-Protocol
encoding	O
(	O
see	O
Figure	O
)	O
where	O
the	O
first	O
component	O
encodes	O
the	O
coverage	O
description	O
(	O
domain	O
extent	O
,	O
range	O
type	O
,	O
metadata	O
,	O
etc	O
.	O
)	O
</s>
<s>
Early	O
GIS	B-Application
systems	O
were	O
often	O
characterised	O
as	O
either	O
'	O
raster	O
 '	O
or	O
'	O
vector	O
 '	O
systems	O
,	O
depending	O
on	O
the	O
underlying	O
approach	O
to	O
handling	O
geometry	O
.	O
</s>
<s>
Raster	O
GIS	B-Application
could	O
be	O
interpreted	O
as	O
using	O
a	O
regular	O
discrete	O
coverage	O
model	O
,	O
while	O
Vector	O
GIS	B-Application
are	O
more	O
feature-oriented	O
.	O
</s>
<s>
The	O
term	O
"	O
coverage	O
"	O
was	O
most	O
notably	O
applied	O
to	O
the	O
legacy	O
ARC/INFO	B-Application
(	O
ArcInfo	B-Application
)	O
format	O
developed	O
by	O
ESRI	O
.	O
</s>
<s>
At	O
that	O
time	O
this	O
was	O
a	O
novel	O
concept	O
,	O
extending	O
CAD	B-Application
formats	O
into	O
more	O
spatially	O
aware	O
data	O
that	O
featured	O
linked	O
attributes	O
.	O
</s>
<s>
This	O
usage	O
was	O
consistent	O
with	O
the	O
coverage	O
concept	O
discussed	O
here	O
,	O
in	O
the	O
sense	O
that	O
an	O
ArcInfo	B-Application
coverage	O
provided	O
a	O
one-to-one	O
mapping	O
from	O
space	O
to	O
the	O
thematic	O
value	O
or	O
classification	O
for	O
each	O
layer	O
or	O
coverage	O
.	O
</s>
<s>
However	O
,	O
ArcInfo	B-Application
coverages	O
had	O
a	O
particular	O
topological	O
approach	O
to	O
ensure	O
completeness	O
and	O
uniqueness	O
,	O
processed	O
using	O
the	O
BUILD	O
and	O
CLEAN	O
commands	O
are	O
2D	O
planar	B-Device
datasets	O
that	O
maintain	O
topological	O
information	O
,	O
thus	O
a	O
polygon	O
"	O
knows	O
"	O
which	O
segments	O
of	O
its	O
perimeter	O
it	O
shares	O
with	O
adjacent	O
polygons	O
.	O
</s>
<s>
Due	O
to	O
the	O
lack	O
of	O
processing	O
power	O
in	O
computing	O
at	O
the	O
time	O
of	O
its	O
development	O
,	O
the	O
Coverage	O
model	O
employs	O
indexed	O
binary	O
files	O
to	O
store	O
spatial	O
and	O
attribute	B-General_Concept
data	O
separately	O
as	O
opposed	O
to	O
utilizing	O
a	O
RDBMS	O
.	O
</s>
<s>
This	O
has	O
changed	O
with	O
the	O
advent	O
of	O
raster	O
database	O
technology	O
like	O
rasdaman	B-Application
which	O
makes	O
efficient	O
ad	O
hoc	O
filtering	O
and	O
processing	O
feasible	O
.	O
</s>
