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Introduction
to SPOT
The first SPOT satellite was launched in 1986 and this
was followed in 1988 by SPOT2, in 1993 by SPOT 3, and in
1998 by SPOT 4. The
latest addition to the series, SPOT 5 was launched on 4th
May 2002 and has increased resolution and spectral capabilities.
The
SPOT satellites have a repeat cycle of 26 days. However,
their sensors can be tilted to view areas that are under
different orbital tracks. This makes it possible to view
specific points
on the earth with a 5-10 day frequency. SPOT satellites
have an onboard tape recorder, as well as a network of ground
stations, so data can be acquired anywhere in the world.
SPOT Imagery
All scenes cover an area of approximately 60x60
km and data can be acquired in black and white or colour
modes. Colour
and b&w data can be recorded simultaneously with the
satellite's two imaging sensors and digitally merged together
e.g. for SPOT-5 to effectively give colour data at both 5m
or 2.5m resolution.
Some selected archived full scene image prices follow. However
images can also be purchased by subscene, or for an additional
800 euros / scene the satellite can be programmed to acquire
new data.
Delivery of archived scenes is approximately 2 weeks.
Satellite programming continues until a scene with less than
10% cloud is recorded. The time taken for an image to be
acquired depends greatly on the local climate and on other
program requests in the area.
It usually takes a few days
to set up the program request and about 10 days or so to
have the data received from the ground
station and processed. Typical programming periods in arid
climates may be 3-4 weeks, 2 months in temperate climates
and several months, dependent on season, in tropical regions.
Images
are recorded at around 10.00 am local time.
Processing and production of hard copy from digital SPOT data
takes approximately 2-5 days. Images can be acquired shifted
north-south along an orbital track for no extra charge.
The largest recommended scale for 2.5m SPOT b&w is 1:10,000
scale. PAN images would typically be used for detecting detail
and structure whereas colour images are particularly useful
for discriminating between land cover types.
Digital Elevation Models
The SPOT 5 satellite has an additional
High Resolution Stereo (HRS) sensor that is used to generate
Digital Elevation Models from along-track stereo imagery.
The stereo imagery from this sensor can not be purchased,
however the DEM cost is 2.3 euros / sq. km for areas of 0
to 3000 sq. km. Vertical accuracy is 15m without ground control
and elevations are computed on a 20m horizontal grid.
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