International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004
deliver near photographic high resolution satellite imagery of
anywhere in the world.
IKONOS imaging system, present three different products: 1-
meter Panchromatic (Pan), 4-meter Multi-spectral (MS), 1-meter
Pan-Sharpened (PSM). Pan-Sharpening combines the spatial
content of the 1-meter panchromatic data with the spectral content
of the 4-meter multi-spectral data. The final product gives a
“color” image at 1-meter resolution, but the MS radiance values
are changed and therefore the product is no longer suitable for
automatic classification (Samadzadegan et.al,2003 ).
Radiometric Resolution: Ikonos data is collected as 11 bits per
pixel (2048 gray tones). This means that there is more definition
in the grey scale values and as a viewer you can see more detail in
an image. In order to benefit from this additional information, it is
required specialist image processing software.
Ikonos has both cross and along track viewing instruments which
enable flexible data acquisitions and frequent revisiting
capabilities - 3 days at 1 metre resolution and 1 to 2 days at 1.5
metre resolution.
Band Width Spatial Resolution
Panchromatic 0.45 - 0.90pm 1 meter
Band 1 0.45 - 0.53pm (blue) 4 meters
Band 2 0.52 - 0.61 um (green) 4 meters
Band 3 0.64 - 0.72um (red) 4 meters
Band 4 0.77 - 0.88um (near infra-red) 4 meters
4. OTHER SATELLITES
4.1 LANDSAT 7
The earth observing instrument on Landsat 7, the Enhanced
Thematic Mapper Plus (ETM+), replicates the capabilities of the
highly successful Thematic Mapper instruments on Landsats 4 and
5% The ETM+ also includes new features that make it a more
versatile and efficient instrument for global change studies, land
cover monitoring and assessment, and large area mapping than its
design forebears. The primary new features on Landsat 7 are:
e a panchromatic band with 15m spatial resolution
e on board, full aperture, 5% absolute radiometric
calibration
e athermal IR channel with 60m spatial resolution
4.2 SPOT 5
Following SPOT 4, the SPOT family provides service continuity
with SPOT 5 for which CNES is designing a new imaging
instrument High Resolution Geometry or HRG. SPOT 5 offers
new capabilities and performance to answer the growing demand
in cartography, agriculture, planning and environment.
SPOT 5 was placed by Ariane in the same orbit as SPOT 1, 2, 3
and 4, i.e. a circular, quasi-polar orbit at an altitude of 830 km and
a pass over the equator at 10.30 a.m. (local time at descending
node). =
The main payload consists of high resolution imaging instruments
delivering the following product improvements compared to
SPOT 4:
e higher ground resolution: 5 meters and 2.5 meters (instead of
10 m) in panchromatic mode,
e higher resolution in multispectral mode: 10 m (instead of 20
m) in all 3 spectral bands in the visible and near infrared
ranges. The spectral band in the intermediate infrared
(essential for Vegetation data) is maintained at a resolution of
20 m due to limitations imposed by the geometry of the CCD
sensors used in this band,
e field width of each instrument: 60 km,
e the oblique viewing capacity of each instrument
maintained, providing rapid access to a given area,
- dedicated instrument for along track stereo acquisition,
S
The Spot 5 spectral bands are the same as those for Spot 4. The
panchromatic band does, however, return to the values used for
Spot 1-2-3 (0,51 - 0,73 um). As requested by many users, this
ensures continuity of the spectral bands established since Spot 1.
Spatial resolutions are, on the other hand, improved within the
limits of technical feasibility as the field width of each instrument
will be also kept identical.
HRG sensors:
Two HRG (High Resolution Geometric) instruments are capable
of generating data at four resolution levels with the same 60 km
swath:
- images in the SWIR band: 20 m
- multispectral images (green, red and near-infra-red): 10 m
- panchromatic images : 5 m
- supermode panchromatic images: 2.5 m
5. HIGH ACCURACY LEVELS TO BE OBTAINED FROM
SATELLITE IMAGES
Now it is possible to generate the thematic maps on various scales
ranging from 1:2500 and 1:1,000,000 scales keeping in view the
end users requirement. The locational accuracy of maps is utmost
important for certain applications like Cadastral survey,
infrastructure/utility maps, Urban land use, Land planning and
Land consolidation works etc. Using one-meter resolution
imagery and GPS controls, it is now possible to achieve an
accuracy of +/- 2 meters. It will be appropriate here to discuss the
technical lag between the large-scale topographic maps on
1:25,000 scale and the utilization of information provided by finer
resolution (around 1 meter) offered by recently launched satellites.
The utility of remotely sensed derived information/maps.
especially from finer resolution satellites can be described in the
context of National Spatial Data Infrastructure. The application
and mapping potential of very high resolution data like IKONOS,
Cartosat etc. is now encourage us to use them in several projects
of different purpose. Some projects studied by researchers
demonstrated the mapping potential of the finer resolution
imagery. Results from such two pilot studies on Large scale
mapping using IKONOS (1 Mt) data represented in Ghosh's paper
(2003) suggest 6 m and 2 m locational accuracy taking controls
from 1:25,000 scale map and GPS based points respectively.
These studies also proved that one could go up to 1:2500 scale
thematic mapping such as urban land use.
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