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There are also a number of advantages that are of enor-
mous significance for practical image application. There is
no need, for instance, to arrange complex and very expen-
sive fly-overs by specialist companies. Images can also be
procured retrospectively and costs per surface unit are
considerably lower. Direct digital registration of image data
can likewise be regarded as a benefit, though with the aid
of DPA (digital photogrammetry assembly) cameras this will
also be possible with aerial-image fly-overs in future.
One disadvantage of satellite image technology at present,
viz. the long repetition times of approx. 24 days, which in
conjunction with the meteorological conditions required for
optical recording processes results in comparatively few
(frequently too few!) usable shots being taken per year, is
set to be rectified, with repetition times of 1-3 days being
targeted (see Table 1).
Up to 1996, it has to be said that developments in the satel-
lite image market were sluggish. The only real innovation,
delivering a geometric resolution of 1-2 metres, were the
photographic images of the Russian KFA-1000 and KVR-
1000 cameras from the Cosmos range, launched in the
early 90s. But since neither continuous data registration nor
reliable distribution could be assured, elementary prerequi-
sites for the operational deployment of these images in
spatial planning were not in place.
The Indian IRS-1C and IRS-1D satellites that have been in
orbit since 1996 and 1997 respectively have ushered in
frenetic developments in satellite-based remote sensing.
Data that can be searched for via the Internet have opened
up radically new areas of resolution and proved, as is
shown below, to be ideal for use in spatial planning. The
recording system was developed specifically with terrestrial
requirements in mind, satellite remote sensing being of the
utmost significance especially for large countries like India
whose national cartographic recording systems are still
relatively speaking in their infancy.
Besides the surge of innovation in the spheres of sensing,
telematics and information-processing technology (proces-
sors, memories, etc.), recent advances in the satellite ima-
ge market are also in the final analysis rooted in the ending
of the Cold War. Technology that was previously reserved
for military defence is now pressing a claim for application
and marketing in the civil sector. The commercialisation of
remote sensing from space that can be discerned is cau-
sing its development to be further accelerated and directly
benefiting the user by leading to more user-friendly satellite
imagery.
In the USA alone, four new commercial suppliers will be
marketing image products over the next two years with a
geometric resolution of between one and five metres. Ta-
ble 1 provides a run-down of the new satellite systems.
Likewise, a major qualitative leap in data marketing is envi-
saged with these data. Image search, selection and sale
will be simplified, rendered more flexible, and significantly
speeded up by the Internet. The new systems will also
make it possible in future to acquire data to order by direc-
ting the sensor at a preselected area. Delivery times (from
recording to supply) will be very markedly reduced (« 2
days) and product prices will also come down further.
Data from the Indian IRS-1C remote sensing satellite are
being assessed within the framework of a project entitled
"Potential uses of the latest high resolution satellite imagery
for regional planning" and funded by the German Research
Community. The area under investigation is the Dresden
urban region and the basis of studies, which commenced in
November 1997, are one panchromatic and one multispec-
tral IRS-1C scene from 16 September 1997.
Company System ISRO Earth Watch Earth Watch Orbimage Space imaging
IRS 1C/1D "EarlyBird" "QuickBird" "Orb-View 3" "IKONOS"
Starting date 1996 1997/98 1999 1/1999 1998
Orbiting height (km) 800 470 470 470 470
Recording modes PAN' MS? PAN' MS? PAN’ MS? PAN' MS? PAN' MS?
Geometric resolution (m) 5.8 23.0 3 15 0.82 3.28 yo 4 1 4
Radiometric resolution (bit) 6 7 8 8 11 11 ? ? 11 11
Spectral resolution 1 34 1 3 1 4 1 4 1 4
(number of channels)
Strip width (km) 70 142 11 55 22 8 11
Repetition rate (days) 24 2-5 1-2 e 1-3
Scale of map 1:25,000 1:15,000 1:5,000 1:5,000 1:5,000
PAN = panchromatic; MS = multispectral
Table 1: New commercial high-resolution satellite sensors
Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 251
