<s>
The	O
Shuttle	B-Algorithm
Radar	I-Algorithm
Topography	I-Algorithm
Mission	I-Algorithm
(	O
SRTM	B-Algorithm
)	O
is	O
an	O
international	O
research	O
effort	O
that	O
obtained	O
digital	B-Application
elevation	I-Application
models	I-Application
on	O
a	O
near-global	O
scale	O
from	O
56°S	O
to	O
60°N	O
,	O
to	O
generate	O
the	O
most	O
complete	O
high-resolution	O
digital	O
topographic	O
database	O
of	O
Earth	O
prior	O
to	O
the	O
release	O
of	O
the	O
ASTER	O
GDEM	O
in	O
2009	O
.	O
</s>
<s>
SRTM	B-Algorithm
consisted	O
of	O
a	O
specially	O
modified	O
radar	B-Application
system	I-Application
that	O
flew	O
on	O
board	O
the	O
Space	O
Shuttle	O
Endeavour	O
during	O
the	O
11-day	O
STS-99	O
mission	O
in	O
February	O
2000	O
.	O
</s>
<s>
The	O
radar	B-Application
system	I-Application
was	O
based	O
on	O
the	O
older	O
Spaceborne	B-Algorithm
Imaging	I-Algorithm
Radar-C/X	I-Algorithm
-band	I-Algorithm
Synthetic	I-Algorithm
Aperture	I-Algorithm
Radar	I-Algorithm
(	O
SIR-C/X	O
-SAR	O
)	O
,	O
previously	O
used	O
on	O
the	O
Shuttle	O
in	O
1994	O
.	O
</s>
<s>
To	O
acquire	O
topographic	O
data	O
,	O
the	O
SRTM	B-Algorithm
payload	O
was	O
outfitted	O
with	O
two	O
radar	B-Application
antennas	O
.	O
</s>
<s>
The	O
technique	O
employed	O
is	O
known	O
as	O
interferometric	O
synthetic	O
aperture	O
radar	B-Application
.	O
</s>
<s>
Intermap	O
Technologies	O
was	O
the	O
prime	O
contractor	O
for	O
processing	O
the	O
interferometric	O
synthetic	O
aperture	O
radar	B-Application
data	O
.	O
</s>
<s>
Each	O
one	O
arcsecond	O
tile	O
has	O
3,601	O
rows	O
,	O
each	O
consisting	O
of	O
3,601	O
16	B-Device
bit	I-Device
bigendian	O
cells	O
.	O
</s>
<s>
The	O
original	O
SRTM	B-Algorithm
elevations	O
were	O
calculated	O
relative	O
to	O
the	O
WGS84	O
ellipsoid	O
and	O
then	O
the	O
EGM96	O
geoid	O
separation	O
values	O
were	O
added	O
to	O
convert	O
to	O
heights	O
relative	O
to	O
the	O
geoid	O
for	O
all	O
the	O
released	O
products	O
.	O
</s>
<s>
The	O
elevation	O
models	O
derived	O
from	O
the	O
SRTM	B-Algorithm
data	O
are	O
used	O
in	O
geographic	B-Application
information	I-Application
systems	I-Application
.	O
</s>
<s>
The	O
Shuttle	B-Algorithm
Radar	I-Algorithm
Topography	I-Algorithm
Mission	I-Algorithm
is	O
an	O
international	O
project	O
spearheaded	O
by	O
the	O
U.S.	O
National	O
Geospatial-Intelligence	O
Agency	O
(	O
NGA	O
)	O
,	O
an	O
agency	O
of	O
the	O
U.S.	O
Department	O
of	O
Defense	O
,	O
and	O
the	O
U.S.	O
National	O
Aeronautics	O
and	O
Space	O
Administration	O
(	O
NASA	O
)	O
.	O
</s>
<s>
NASA	O
transferred	O
the	O
SRTM	B-Algorithm
payload	O
to	O
the	O
Smithsonian	O
National	O
Air	O
and	O
Space	O
Museum	O
in	O
2003	O
;	O
the	O
canister	O
,	O
mast	O
,	O
and	O
antenna	O
are	O
now	O
on	O
display	O
at	O
the	O
Steven	O
F	O
.	O
Udvar-Hazy	O
Center	O
in	O
Chantilly	O
,	O
Virginia	O
.	O
</s>
<s>
The	O
USGS	O
SRTM	B-Algorithm
data	O
is	O
based	O
on	O
NASA	O
's	O
SIR-C	O
instrument	O
.	O
</s>
<s>
Version	O
3	O
(	O
2013	O
)	O
,	O
also	O
known	O
as	O
SRTM	B-Algorithm
Plus	O
,	O
is	O
void-filled	O
with	O
ASTER	O
GDEM	O
and	O
USGS	O
GMTED2010	O
.	O
</s>
<s>
The	O
SRTM	B-Algorithm
also	O
carries	O
the	O
X-SAR	O
instrument	O
operated	O
by	O
the	O
German	O
Aerospace	O
Center	O
(	O
DLR	O
)	O
and	O
Italian	O
Space	O
Agency	O
(	O
ASI	O
)	O
.	O
</s>
<s>
The	O
resulting	O
dataset	O
is	O
usually	O
called	O
SRTM/X	O
-SAR	O
,	O
or	O
SRTMX	O
for	O
short	O
.	O
</s>
<s>
There	O
are	O
some	O
SRTM	B-Algorithm
data	O
sources	O
which	O
have	O
filled	O
these	O
data	O
voids	O
,	O
but	O
some	O
of	O
these	O
have	O
used	O
only	O
interpolation	B-Algorithm
from	O
surrounding	O
data	O
,	O
and	O
may	O
therefore	O
be	O
very	O
inaccurate	O
.	O
</s>
<s>
If	O
the	O
voids	O
are	O
large	O
,	O
or	O
completely	O
cover	O
summit	O
or	O
ridge	O
areas	O
,	O
no	O
interpolation	B-Algorithm
algorithms	O
will	O
give	O
satisfactory	O
results	O
.	O
</s>
<s>
Groups	O
of	O
scientists	O
have	O
worked	O
on	O
algorithms	O
to	O
fill	O
the	O
voids	O
of	O
the	O
original	O
SRTM	B-Algorithm
(	O
v2.1	O
)	O
data	O
.	O
</s>
<s>
Three	O
datasets	O
offer	O
global	O
coverage	O
void-filled	O
SRTM	B-Algorithm
data	O
at	O
full	O
(	O
3-arcsecond	O
)	O
resolution	O
:	O
</s>
<s>
The	O
CGIAR-CSI	O
version	O
4	O
provides	O
the	O
best	O
global	O
coverage	O
using	O
interpolation	B-Algorithm
.	O
</s>
<s>
The	O
void-filled	O
SRTM	B-Algorithm
data	O
from	O
Viewfinder	O
Panoramas	O
by	O
Jonathan	O
de	O
Ferranti	O
are	O
high	O
quality	O
at	O
full	O
SRTM	B-Algorithm
resolution	O
.	O
</s>
<s>
In	O
November	O
2013	O
,	O
LP	O
DAAC	O
released	O
the	O
NASA	O
Shuttle	B-Algorithm
Radar	I-Algorithm
Topography	I-Algorithm
Mission	I-Algorithm
(	O
SRTM	B-Algorithm
)	O
Version	O
3.0	O
(	O
SRTM	B-Algorithm
Plus	O
)	O
Product	O
collection	O
with	O
all	O
voids	O
eliminated	O
.	O
</s>
<s>
1-arc	O
second	O
global	O
digital	B-Application
elevation	I-Application
model	I-Application
(	O
30	O
meters	O
)	O
is	O
available	O
from	O
the	O
United	O
States	O
Geological	O
Survey	O
web	O
site	O
.	O
</s>
<s>
The	O
United	O
States	O
Government	O
announced	O
on	O
September	O
23	O
,	O
2014	O
over	O
a	O
United	O
Nations	O
Climate	O
Summit	O
that	O
the	O
highest	O
possible	O
resolution	O
of	O
global	O
topographic	O
data	O
derived	O
from	O
the	O
SRTM	B-Algorithm
mission	O
will	O
be	O
released	O
to	O
public	O
.	O
</s>
<s>
Before	O
the	O
end	O
of	O
the	O
same	O
year	O
,	O
a	O
1-arc	O
second	O
global	O
digital	B-Application
elevation	I-Application
model	I-Application
(	O
30	O
meters	O
)	O
was	O
released	O
.	O
</s>
<s>
In	O
early	O
June	O
2011	O
,	O
there	O
were	O
750,000	O
confirmed	O
users	O
of	O
SRTM	B-Algorithm
topography	O
dataset	O
.	O
</s>
